Alastair Denniston

Notes

Chapter 1: A life in signals intelligence

1. Attributed to a comment by Garnett Wolseley in discussion about a lecture by Major C.F. Beresford, ‘Tactics as Affected by Field Telegraphy’, Journal of the Royal United Service Institute, Vol. 31 (1887), p. 591.

2. Memorandum by G-2, GHQ, undated but c. 1945, ‘The Use of Ultra by the Army’, WO 208/3575.

3. National Army Museum (NAM), Leith-Ross papers, 8312-69, ‘The Strategical Side of 1(a)’, undated and unsigned but Spring 1919 according to internal evidence and presumably by Leith-Ross.

4. Intelligence Corps Museum (CM), Kirke papers, Accession Volume 58, notes for lecture by Kirke, 27 November 1925.

5. Friedman’s lectures were also published by the NSA for the first time in 1963 and reprinted in 1965 to help provide an authoritative history of the subject. The latest version was published in 2006 by the NSA’s Center for Cryptologic History – see bibliography.

6. James Thurloe had been granted control of both Inland and Continental postal offices through a so-called farming system at an annual rent of £10,000 per year in 1655 and retained control after his appointment. He was Secretary of the Council of State from 1652 to 1659 and MP for Ely from 1654 to 1655 and 1656 to 1658.

7. Isaac Dorislaus was the son of the ambassador to Holland and served in the post from 1653 to 1681 and possible until his death in 1688. He was paid £200 per year as Solicitor to the Admiralty from 1653 to 1660 and afterwards, £220 per year, issued to the Secretaries of State from the Post Office revenue.

8. John Wallis was born in 1616 and started his career in cryptography by deciphering the King’s dispatches for parliament in 1643. He was appointed Secretary to the Westminster Assembly in 1644 and Savilian Professor of Geometry at Oxford in 1649. Together with his work on conic sections, Wallis published the book on which his fame as a mathematician is based, Arithmetica infinitorum, in 1656.

9. Commons Debates lxxv (1844), 1291. Similar sentiments were expressed by the US Secretary of State, Henry Stimson, who closed down the US Army’s codebreaking section, the Black Chamber. Years later in his memoirs, Stimson made the frequently quoted comment, ‘Gentlemen do not read each other’s mail.’

10. In the latter part of WW2, Hitler’s cryptography experts wanted to replace the Enigma en masse with the more secure SG-41 cipher machine. However, by that time there were tens of thousands of Enigmas in service. In mid-1944, the German Supreme Command ordered a procurement of 11,000 SG-41 machines for the Armed Forces. Despite these large orders, only about 500 units of the SG-41 were delivered, mainly due to the production problems experienced during the last two years of the war and operators finding the machine difficult to use. See Klaus Schmeh, http://www.heise.de/tp/artikel/

11. ADM 137/4701, Intelligence E(C) to G.S.I. e., 10 October 1918.

12. See Ferris, ‘The British Army and Signals Intelligence in the Field During the First World War’.

13. The British Red Cross is part of the International Red Cross and Red Crescent Movement, the world’s largest independent humanitarian network. The Red Cross and Red Crescent Movement is made up of three parts: the International Committee of the Red Cross (ICRC); the International Federation of Red Cross and Red Crescent Societies; 190 National Red Cross and Red Crescent Societies around the world, including the British Red Cross.

14. He was awarded the Star of the Third Order of the Osmauli and the Star of the Third Order of the Medjidie and with the war medal for the Serbian campaign.

15. Merchiston Castle was the former home of John Napier, the inventor of logarithms.

16. James Alfred Ewing was born in Dundee in 1855 and went from Dundee High School on a scholarship to Edinburgh University in 1872. He studied engineering under Fleeming Jenkin, Professor of Engineering. Jenkin was remarkable for the versatility of his talent. Known to the world as the inventor of Telpherage (a transportation system in which cars [telphers] are suspended from cables and operated on electricity), he was an electrician and cable engineer of the first rank, a lucid lecturer, and a good linguist, a skilful critic, a writer of and actor in plays, and a clever sketcher. Jenkin sent Ewing to South America in 1874 to work on a cable to Montevideo and while doing this work, Ewing became interested in devising telegraphic codes. He returned to Edinburgh in 1876 to take his degree and two years later accepted the new Chair of Mechanical Engineering in the University of Tokyo. In 1887 he returned to Dundee as Professor of Engineering at the new University College and in 1890 went to Cambridge as Professor of Mechanism and Applied Mechanics.

17. Fisher was appointed First Sea Lord at the end of October 1914 even though he was in his seventies. He had previously served in the role from 21 October 1904 until 25 January 1910. He served until 15 May 1915 when he was replaced by Admiral Sir Henry Jackson who served until 30 November 1916. Jackson in turn was replaced by Admiral of the Fleet Sir John Jellicoe who served until 10 January 1918. His successor, Admiral of the Fleet Sir Rosslyn Wemyss, served until 1 November 1919.

18. By the end of 1919 the Admiralty had decided to abolish Osborne, take in boys at 13, give them three years at Dartmouth, then a year in a cruiser. The winding down of the college began at the end of 1920 and it finally closed on 20 May 1921.

19. See Partridge, p. 17.

20. The Osborne Lists are a record of staff at the College and some of these are held in the Archive of the Britannia Royal Naval College in Dartmouth. The Navy Lists are of naval personnel including those at educational establishments. The latter are also held in Dartmouth.

21. A selection of the Osborne College magazines are held in the Archive of the Britannia Royal Naval College in Dartmouth.

22. See Partridge, p. 53.

23. Custance Committee, Fourth Report, 20 September 2012, Inclosure 9, The National Archives (TNA) ADM116/1288.

24. Godfrey’s brother John would serve as DNI from 1939 to 1942.

25. A series of figures, numbers or letters which are used in the encryption/encipherment and decryption/decipherment of messages in a given cipher system.

26. A Watch usually consisted of a group of men (watchkeepers) tasked with translating and analysing incoming enemy traffic. The term originated in the Royal Navy system which linked a group of personnel to a period of time.

27. Treasury file T1/11937.

28. DENN 1/2, Churchill College Archive, Cambridge.

29. A group usually of three or more letters and/or figures, sent either in clear or in cipher, either in the preamble or in the body of a message, and serving to identify the sender and/or the recipient.

30. DENN 1/2, Churchill College Archive, Cambridge.

Chapter 2: British sigint in World War one

1. Two hundred and fifteen wireless stations have been documented in an English Heritage report as follows: eighty-seven coastal wireless (W/T) and/or intercept sites; twenty-two Royal Flying Corps (RFC) home defence sites; forty-one Royal Naval Air Service( RNAS) aerodrome sites; fifty-two RFC aerodrome sites; seven lightship sites; six experimental/portable sites. See First World War Wireless Stations in England. English Heritage Report, January 2015.

2. This is generally considered to be a fable of Churchill’s.

3. See Hammant.

4. All three German systems: the naval code proper (the three-letter Signalbuch der Kaiserlichen Marine); the four-letter Handelsverkehrsbuch, used by both naval and merchant vessels; a five-figure naval attaché cipher (the Verkehrsbuch) fell into British hands early in the war but their successors were broken through cryptanalysis. All code books were alphabetical until 1917 when the Signalbuch was replaced by the three-letter ‘hatted’ Flottenfunkspruchbuch (FFB). While other complications were introduced, Room 40 gradually mastered most German naval cryptographic methods. The main limitation was the volume of messages which could be intercepted at the Y stations at Hunstanton (HQ), Mercar in Aberdeen, Stockton-on-Tees and Cambridge.

5. DENN 1/2, Churchill College Archive, Cambridge.

6. This view was taken by historians because MI1(b)’s contribution to diplomatic Sigint had been forgotten.

7. This is probably Admiral Sir Sydney Fremantle, who was assigned to the Signal Division in the Admiralty and responsible for compiling secure code and cipher books. See Fremantle, p. 172.

8. See Ewing, The Man of Room 40.

9. Oliver had been Director of the Intelligence Division (DID), the senior Division of the Naval Staff. His taciturn manner resulted in the nickname ‘Dummy’ and he was apparently very poorly dressed. He was a hard worker and former Admiral of the Fleet who lived to the age of 100. His principal deputy was Captain Thomas Jackson, Director of the Operations Division (DOD).

10. Admiral Sir Arthur Wilson, a former First Sea Lord and before that, Commander-in-Chief of the Channel Fleet. Retired in 1912 at 70 but returned in an unofficial and unpaid capacity in November 1914 to help his friend, Oliver. Dedicated and tough, he was known on the Lower Deck as ‘Old ‘Ard ‘Art’.

11. See Churchill, Vol. 1, p. 361.

12. Hall was born at Britford, Wiltshire, on 28 June 1870. He was the elder son of Captain William Henry Hall, RN, the first Director of the Intelligence Division at the Admiralty. The Admiralty Board decided to set up a section under Hall Sr. in 1882 to collect and sift reports from abroad and to provide them with up-to-date information about foreign fleets in the event of potential conflict. Hall Jr signed on in 1884 and after rising through the ranks, was promoted to Commander in 1901 and appointed to HMS Magnificent, flagship of the Second-in-Command, Channel Fleet. He was promoted to captain in 1905 and installed by the First Sea Lord, Sir John Fisher, as Inspecting Captain of the new Mechanical Training Establishment. In 1913 he was appointed captain of the new battlecruiser Queen Mary. The British naval historian Patrick Beesly met Hall once and provides a colourful description of him. See Beesly, p. 36.

13. Ewing had been made a Commander of the Bath in 1906 and Knight Commander of the Order in 1911.

14. GCHQ is in possession of two 1907 reports from Simla dealing with Russian ciphers which provide a useful insight into modern Sigint. They were distributed to headquarters in India and via the India Office to the War Office and possibly the Admiralty.

15. This system was probably the German training cipher known from the discriminant used in exercise traffic as ÜBCHI (Übungschiffrierung). MO5 had obtained a German army staff manual before the war and it was studied for ‘many weary hours’ by Major Walter Kirke, Macdonagh’s assistant in the ‘Special Section’.

16. John Ferris, ‘The British Army and Signals Intelligence in the Field during the First World War,’ Intelligence and National Security, 3/4 (1988).

17. Intelligence E (c) to G.S.I.e, 10.10.18, TNA ADM 137/4701.

18. The only primary sources available are: three folders of MI1(b)’s own papers, a few MI1(b) diplomatic decrypts and information on its 1919 work and staffing recorded in the course of the discussions about establishing GC&CS; History of MI1(b), HW7/35 written between November 1919 and January 1923 (it is quoted in a War Office paper of that date ‘History of the Cryptographic and Wireless Intelligence Organisation’, HW 3/39) possibly by Maj. G.L. Brooke-Hunt); Hay’s notes and his wife’s book.

19. The War Office destroyed the relevant records after the end of the war. It is likely that as in Aden, cryptanalysis was used to detect attempts to evade censorship.

20. This was the so-called ADFGVX cipher, a complicated combination of substitution and transposition with frequently-changing keys.

21. Macdonagh would later serve as DMI from January 1916 until September 1918.

22. The MI1(b) files were destroyed during the Blitz, along with the rest of the War Office’s intelligence archives, and those of other arms of service as well.

23. Hay would later contest with AGD for a new post which would head a combined army/navy intelligence section. He would also go on to be an eminent historian, publishing a number of major historical works. Hay was admired by his staff and considered to be a good chief and was given charge of constructing codes and ciphers for British forces early in 1917.

24. A ‘crib’ is a guessed word or phrase contained within an encrypted message.

25. See Alice Hay.

26. History of MI1(b), TNA HW 7/35, written between November 1919 and January 1923 (it is quoted in a War Office paper of that date (History of the Cryptographic and Wireless Intelligence Organisation, TNA HW 3/39)).

27. Hay made notes for much of the war which were published in a biography by his widow in 1971, together with some of her own views. See Alice Hay. The earliest surviving American telegram is from their Ambassador in London to Washington, sent on 23 January 1916. (TNA HW 7/17)

28. History of MI1(b).

29. Ibid.

30. Regrettably, while the Admiralty preserved the archives of Room 40, the Army chose to destroy most of the original intelligence files of MI1(b). Only twenty-five of the 3,330 (at least) files of codebreakers at GHQ France survive. Only four of the 400 weekly reports of the codebreakers in the Middle East on traffic analysis and cryptanalysis survive.

31. DENN 1/3, also DENN 1/2, Churchill College Cambridge Archive Centre (CCAC). Some messages dated between August 1915 and January 1916 are available at TNA (HW 7/5, HW 7/6). Around five of the thirty staff were working on German diplomatic messages (similar to MO6(b)’s effort against American telegrams).

32. TNA HW 3/184.

33. Ibid.

34. See Hay.

35. One of the most skilled MI1(b) cryptanalysts was Captain G.L. Brooke-Hunt. He solved the so-called FürGOD cipher in early 1917 which was used for messages sent around three times a week from a powerful German station at Nauen outside Berlin to German wireless stations with the callsign GOD. A message arranging for a submarine to bring rifles and ammunition to a Moroccan nationalist was passed to Hall at the Admiralty and the submarine was duly intercepted and sunk.

36. A hatted code is arranged in other than numerical (or alphabetical) order. A ‘hat code-book’ is characterized by the fact that when the plain-language terms are arranged in alphabetical order the code groups are not in numerical (or alphabetical) order; i.e. a two-part code. A recipherment conceals the true character and figures or letters of an encoded message by applying a key or subtractor (usually by non-carrying addition or subtraction) or by any system of transposition or substitution.

37. These were standard in format throughout the armies and similar to those still used in WW2, but easily modified locally by changing meanings or by encryptment. They consisted of trinomes or trigraphs together with encipherment tables. Similar codes were used for air-to-ground communications.

38. DENN 1/2, Churchill College Archive, Cambridge.

39. See Appendix 1. GCHQ regard this as their own charter document.

40. Admiral of the Fleet Sir Henry Oliver, ‘Recollections’, National Maritime Museum, OLV 12.

41. The Heligoland Bight is a stretch of water off Germany’s main North Sea naval base of Wilhelmshaven, a coastal town in Lower Saxony.

42. DENN 1/2, Churchill College Archive, Cambridge.

43. Ibid.

44. Churchill, Vol. I, p. 115

45. DENN 1/2, Churchill College Archive, Cambridge.

46. Ibid.

47. ‘Dilly’ Knox was one of four sons of the Bishop of Manchester. Of his brothers, Edmund became editor of Punch magazine, Wilfred was a Church of England theologian and Ronald was a Catholic clergyman who translated the New Testament for Catholics.

48. See Fitzgerald on the Knox brothers.

49. Frank Birch had enlisted in the RNVR at the outbreak of war and served at sea in the Atlantic and at the Dardanelles. He was a Fellow at King’s from 1915 to 1934 and a lecturer in History from 1915 to 1928. In the 1930s he left Cambridge to work in the theatre. He worked in Room 40 from 1916 to 1919 and was Head of the Naval Section at BP during WW2 from 1942 to 1945.

50. Frank Adcock had become a King’s Fellow in 1911 and held the Chair of Ancient History from 1925 to 1951. He came from a Methodist background and excelled academically.

51. Montgomery was 44 and the author of studies of St Augustine and a translator of Albert Schweitzer.

52. De Grey was a favourite of Hall, and went on to take charge of the Mediterranean Section. He had studied languages and was fluent in French and German.

53. Clarke is the source of much of the information about recruits to Room 40. See CLKE 1 ,2 and 3, Churchill College Archive, Cambridge.

54. DENN 1/2, Churchill College Archive, Cambridge.

55. See Churchill, Vol. 1, p. 414.

56. Ibid., p. 500.

57. The Dogger Bank is a large sandbank in a shallow area of the North Sea about 100km off the east coast of England.

58. See Churchill, Vol. 1, p. 559.

59. Ibid., p. 560.

60. Ibid., p. 264.

61. Ibid., p. 175.

62. See Ewing, The Man of Room 40.

63. AGD and Clarke, the two chroniclers of Room 40, never offered a complimentary assessment of Ewing’s contribution and it appears he was not held in the highest regard. He presided over Edinburgh University until his retirement in 1929 and died in 1935.

64. Clarke papers, Churchill College, Cambridge.

65. The Zimmermann Telegram has been written about by numerous authors. James claimed his account was the first, probably followed by Hendrick. Friedman and Mendelsohn’s account is considered by most historians to be close to definitive. Barbara Tuchman wrote an entire book on the subject and more accounts have been provided by Beesly, Gannon and Ramsay. Friedman was still querying aspects of it with AGD in the 1960s.

66. Code 7500 was one of a series of two-part codes used by the Germans. The two parts consist of 1) a set of 10,000 phrases in alphabetic order and numbered from 0000 to 9999, the numbers being entirely mixed up so that they have no numerical sequence; and 2), the same phrases fitted with the same numbers as before, but this time with the numbers in sequence and the phrases mixed up. The first part is used for encrypting, i.e. sending a message, the second for decrypting, i.e. reading a message.

67. This route was revealed during an elaborate investigation by the German Constituent Assembly in 1919-20 into the responsibility for the war and the part played by the Zimmermann Telegram. Among its published documents is a note which reveals the other route used by the German Foreign Office (Vol. II, p. 1337, ‘Official German Documents Relating to the World War’. Translated under the supervision of the Carnegie Endowment for International Peace, Division of International Law). ‘Instructions to Minister v. Eckardt were to be taken by letter by way of Washington by U-Boat on the 15th January; Since the U-Boat Deutschland did not start on her outward trip, these instructions were attached on January 16 to telegram No. 157, and through the offices of the American Embassy in Berlin telegraphed to Count Bernstorff by way of the State Department in Washington’. The German Government frequently used the American State Department to send messages to its Ambassador Bernstorff as it had no cable links to the US. They went through British cable facilities and the British didn’t mind as they could read all of the traffic. The messages should have been handed to the American Embassy in plain text to be enciphered with an American code before transmission. However, President Wilson, who was in effect, his own Secretary of State, allowed messages to be handed in already in code on the basis that they were in aid of peace initiatives. The Zimmermann telegram was attached to a message which did pertain indirectly to peace efforts in a very indirect fashion. The German Government was informing its Ambassador that it ‘promises the early termination of the war and the restoration of that peace which the President has so much at heart’. It proposed to bring about this peace by the institution of unrestricted submarine warfare!! Bernstorff was sent the message on 16 January and told not to inform Washington until 1 February. The Zimmermann telegram was attached to this message (No. 157), put into German cipher and handed to US Ambassador Gerard in Berlin. He telegraphed it to Copenhagen, it then went on to London and finally to the State Department in Washington from where it was delivered to Bernstorff.

68. Code 13040 was an old German diplomatic code which was partially mixed up. The alphabetic vocabulary was broken up into fractions and these in turn into smaller fractions before numerical code groups were attached. However, the original alphabetic sequence of the words and phrases was only partially destroyed. This provided helpful clues when decrypting messages encrypted with the code.

69. A third possible route for the Zimmermann Telegram was by radio between the German station at Nauen and one of two American radio stations at Sayville, Long Island and Tuckerton, New Jersey. See Hendrick, Ewing, James and Tuchman who supported this. While now generally dismissed by historians today, it would be the subject of lengthy discussions between AGD and William Friedman fifty years later.

70. TNA HW 3/177 p. 2

71. HALL 3/6, p. 10, Churchill College Archive, Cambridge.

72. Walter Page was born on 15 August 1855. He worked hard to maintain close relations between the US and Great Britain while the US remained neutral. From an early stage of the war, he urged US intervention on an unwilling President Woodrow Wilson. When the British liner Lusitania was sunk by a German submarine (7 May 1915), with the loss of more than 100 American lives, Page called for a US declaration of war. He insisted then and later that US intervention at that time would have resulted in a swift victory for the Allies. In April 1917, when Wilson did ask Congress to declare war on Germany, he used the arguments that Page had been using for two-and-a-half years. Page became ill in August 1918 and retired. He died shortly after returning to the US on 21 December 1918.

73. Wiseman was a member of the Purchasing Commission of the British Ministry of Munitions. His duties also included intelligence and counter-espionage. (See Hyde, p. 63.)

74. The decoded message actually changes handwriting after a few groups, presumably from Bell’s to that of de Grey’s.

75. Edward Mandell House was an American diplomat and confidential advisor to President Woodrow Wilson. He played a key role in formulating the conditions of peace to end WWI.

76. According to a biological sketch, published by the NSA: ‘William Frederick Friedman (1891–1969), the dean of modern American cryptologists, was the most eminent pioneer in the application of scientific principles to cryptology and laid the foundations for presentday cryptologic concepts. He retired from the National Security Agency in 1955 after thirtyfive years of service with US cryptologic activities.

77. See Kahn’s paper in INS which provides the only source of biographical information on Bell.

78. Harrison was partly educated at Eton and considered to be an anglophile. He was Secretary in the Diplomatic Service and assigned to the State Department. He became Assistant Secretary of State in 1922.

79. Correspondence of Leland Harrison with Edward Bell, 12/154/1916 – 7/8/1918, Department of State, Office of the Counsellor 1909-1919, Record Group 59: General Records of the Department of State, 1763 – 2002.

80. See Yardley.

81. See for example Beesly, Room 40.

82. NID Vol. 26. The memorandum is reproduced in facing p. 18.

83. ‘A Contribution to the History of German Naval Warfare, 1914-1918’, Vol. I, pp. 39, TNA H/W 7/1.

84. ‘Thus was built up in the end a system by which momentary or ‘action’ Intelligence could go hand in hand with cumulative or ‘deferred’ Intelligence, and both be singly or together at the immediate disposal of the authorities.’ (A Contribution to the History of German Naval Warfare, 1914-1918, Vol. I, pp. 48, TNA H/W 7/1).

85. Roskill, pp. 145–6; Churchill, Vol. I, p. 466.

86. CLKE 3, Churchill College Archive, Cambridge.

87. See Fraser.

88. See Clarke.

89. James’ biography of Sir Reginald Hall in 1955 is one of the earliest published accounts of the activities of Room 40.

90. Navy List for October 1917. Even though the seniority of the rank is listed as temporary, AGD is still listed as a Commander in the RNVR in January 1920.

91. Hall was elected to Parliament in 1919 and took his seat on 13 March as the MP for the West Derby Division of Liverpool. In October 1919 the University of Cambridge conferred on him the degree of LLD and later Oxford University conferred on him the Honorary Degree of DCL. He died on 22 October 1943.

92. See Churchill, Vol. I.

93. See Scheer.

94. Lecture by Major General D.E. Nolan, 20.3.33, Curriculum Archives, 392-A-19, United States Army Military History Institute, Carlisle Barracks.

95. Barker, p. 180.

96. Memorandum by I9e, ‘Enemy Codes and their Solutions’, I.18, TNA ADM 137/4660.

97. Memorandum by Second Army Intelligence, 1.12.18, AIR 1/2268/209/70/200; memorandum for Chief, Intelligence Section, AEF, 1.1.18. A.L. Conger papers.

98. WO 157/164. 3rd Army Intelligence summary, 14 Aug. 1918 (including order by Ludendorff, 19 Dec. 1917).

99. Notes and Records of the Royal Society of London, Vol. 34, No. 1 (July 1979).

Chapter 3: Between the Wars

1. DENN 4/2, Churchill College Archive, Cambridge.

2. An Anglo-French author, journalist and diplomat who wrote a number of books involving international intrigue.

3. Thwaites to Hall, 14 November 1918; Hall to Thwaites, 26 November 1918; Thwaites to Hall, 28 November 1918, WO32/21380.

4. Field Marshal Sir Henry Wilson was Chief of the Imperial General Staff in 1918, the professional head of the British Army.

5. See Alice Hay.

6. Ibid.

7. TNA HW 3/1.

8. Sinclair was a career sailor who had been educated at the Britannia Naval College at Dartmouth, entering the navy as a midshipman in 1888. His service record indicated that his ability and professional knowledge was ‘very good’ and other positive comments included: ‘steady and trustworthy’; ‘zealous & capable’; ‘Excellent tact & temper’; ‘Very discrete & loyal; exceptional powers of administration’ (Sinclair service record, TNA ADM 196/43). He served in the Mobilisation Division of the Admiralty during WW1 and by its conclusion, was chief of staff of the Battlecruiser Fleet. In January 1919, he succeeded Hall as DNI. Hall was pleased and told Sinclair that it was ‘not often given to men that they see their job filled by the only man who can do it’. (Hall to Sinclair, 18 December 1918 and 14 January 1919, Sinclair papers MS 81/091, scrapbook vol. 1). His stay in Naval Intelligence ended after eighteen months when in August 1921 he was appointed to a three-year post as Rear Admiral ‘S’ (commander of the Submarine Service). However, by the late Spring of 1923, it was decided that he should take over from Cumming, whose health was failing, as Chief of SIS in September of that year. Following Cumming’s death on 14 June, he took up his new post on 3 September.

9. Rotter and Hope had better claims to be the Admiralty candidate but both were moving on. Other civilian members of Room 40 were keen to return to life outside the Service.

10. Curzon to Walter Long, First Lord of the Admiralty, 24 March; minute by Sinclair, 28 March; minutes of conference held at the Foreign Office, 29 April1919, TNA, ADM 1/8637/55.

11. TNA HW 3/35. Notes of Formation of GC&CS TNA HW 3/33.

12. It seems highly unlikely that the Admiralty would have accepted a non-Room 40 candidate.

13. See Alice Hay.

14. Hay’s OBE was actually gazetted, i.e. announced in a Government publication.

15. Establishment of GC&CS covered in TNA HW 3/34 and ADM 1/8637/55.

16. Edward Wilfrid Harry Travis was born on 24 September 1888 in Kent. He was known as Wilfrid to his family and ‘Jumbo’ to friends due to his rather rotund build. He joined the Royal Navy in 1906 and passed to Paymaster in 1909. On the first day of WW1 he was posted as Secretary’s Clerk to the Commander-in-Chief, Admiral Sir John Jellicoe, on the flagship HMS Iron Duke. His 1918 report signed by Jellicoe refers to his zeal, ingenuity and ability. He was lent to the Admiralty’s Signal Division in 1916 at Jellicoe’s request ‘for the compilation of cyphers for use in the Fleet’. It is said that he got this posting because he had personally broken Jellicoe’s ciphers to show their vulnerability.

17. TNA HW 12/1-3.

18. Code and Cypher School memo by Lord Curzon (C.P. 3105), 3 July 1921 (Curzon papers, Mss Eur/ F.112/302).

19. The ‘Geddes Axe’ refers to proposals for spending cuts in Britain, made by Sir Eric Geddes who had been Director-General of Munitions and Railways in WW1, and later Minister of Transport (1919–21). In 1921, He chaired a committee which would suggest reductions in public expenditure of £86 million. The eventual reduction in the 1922 budget was £64 million and Geddes specifically targeted the armed forces, whom he had successfully portrayed as profligate spenders

20. By the late spring of 1923, it was decided that Sinclair should take over from Cumming, whose health was failing, as Chief of SIS in September of that year. Following Cumming’s death on 14 June, he took up his new post on 3 September. Sinclair was a bon vivant whose nickname ‘Quex’ was given to him as a young man and taken from a play by Arthur Pinero called The Gay Lord Quex, in which the hero was described as ‘the wickedest man in London’ who subsequently became a reformed character. According to Jeffrey’s Official History of MI6, he was ‘one of the most imperturbable of men’ and was ‘always appreciative of good service in a subordinate’. He had a stormy private life and had violent rows with his wife in the captain’s cabin while serving as captain of HMS Renown. Much to his embarrassment he was divorced in 1920, soon after becoming naval aide to the King (Andrew, Secret Service, p. 295 and Sinclair service record, TNA ADM 196/43, p. 368, ADM 196/53, p. 199).

21. See Appendix 2 for GC&CS staff list for 1919 (Curzon to Lee, 25 April; and reply 23 May; minute by Lee, 2 May 1921, TNA, Foreign Office 366/800).

22. Report of Inter-Service Directorate Committee, 9 April 1923; note on ‘control of interception’, n.d. [c. 1924] TNA, WO 32/4897.

23. The wartime WOGs had in effect become local Sigint organisations, capable of providing a service to the local commander.

24. The Government Code and Cypher School: A Memorandum by Lord Curzon, CAB 24/126.

25. DENN 1/3.

26. Sinclair to Crowe, 3 November 1923, TNA, Foreign Office 366/800.

27. See Jeffrey, pp. 213–14. His source referenced as ‘Denniston, “Government and Code Cypher School”, 49’.

28. GC&CS ‘Historical Notes’.

29. TNA HW 42/1, HW 42/2, HW 42/30.

30. TNA HW 62/20, HW 62/21.

31. H.C. Kenworthy , ‘A Brief History of Events Relating to the Growth of the ‘Y’ Service’, 11 June 1957, TNA HW 3/81.

32. See Clarke’s memoirs at Churchill College and ‘Naval Section 1927-1939 – Mr W. Bodsworth’s account’, n.d., TNA HW 3/1.

33. Menzies was born on 30 January 1890 in London. He joined the Life Guards in 1910. He served on the Western Front and was decorated for gallantry before being gassed. He was then appointed to a security intelligence position at GHQ and by 1918 he was a liaison officer between the Directorate of Military Intelligence and MI1(c). While in principle a member of the army, who paid his wages, he was a part of ‘C’’s organisation and formally transferred from the War Office to the SIS payroll on 1 April 1923 as Head of Military Section IV. He represented SIS in collaboration with the main French intelligence agency in the 1920s, the Deuxième Bureau. Menzies was fluent in French and this would stand him in good stead in the years leading up to WW2.

34. DENN 1/4.

35. A One-Time Pad disguises the numerical codegroups of a diplomatic or military code by adding them to a long numerical key. The German diplomatic system consisted of pads of fifty numbered sheets, each with forty-eight five-digit groups, distributed in eight lines of six groups. All the digits on each sheet were random, no sheet was duplicated and each sheet was used only once. For example, the code 3043 9710 3964 3043 might have the key 7260 0940 5169 4174 added to it yielding 0203 9650 8023 7117 (no carry over or tens digits are carried or written down so for the first digit in the example above, 3+7 = 10 becomes 0).

36. A slip is a sheet of paper containing a short description of a particular code or cipher system with details of its external characteristics (e.g. call-signs, preamble, etc.), users and period of currency.

37. John Tiltman could lay claim to being one of the greatest cryptologists of his generation. Born in 1894, he was offered a place at Oxford when he was 13 but as his father had recently died, he left school at the end of 1911 to become a teacher. Following a distinguished career in WWI, he was sent on an elementary Russian language course which would change his life. On 1 August 1920, he was seconded for two weeks to GC&CS to help with a backlog of translation work. He took to decryption work so well that the War Office posted him to GC&CS initially for a year but he never returned to conventional regimental duties. A biography of Tiltman is long overdue and his accomplishments are too numerous to cover here. He continued working for GCHQ after the war until his retirement in 1964. He was immediately asked to join the NSA as he was living in the US, and served until 1980 when he was 86! He was honoured by the directors of GCHQ and NSA for his ‘uncountable contributions and successes in cryptology’ and for setting ‘exemplary standards of professionalism and performance in cryptology’.

38. The correct spelling is Vetterlein but official British Government documents of the day use Fetterlein.

39. TNA HW 25/6. Some authors have mistakenly credited ‘Dilly’ Knox with purchasing the machine in the 1920s.

40. Dorothy Denniston’s pass, providing access to the Anglo-French decryption unit at the Paris Peace Conference, is on display at Bletchley Park.

41. ‘Experience 1920-1939’, Brigadier John Tiltman, NSA website, DOCID: 3868631.

42. DENN 1/4.

43. Ibid.

44. DENN 1/4.

45. A small Metropolitan Police wireless unit was initially based in the attic at Scotland Yard and, from the mid-1930s, in the grounds of the Metropolitan Police Nursing Home at Denmark Hill, South London.

46. This was the commercial Enigma with (IIRC) rewired rotors and could be solved using the notes left by Hugh Foss, who had investigated the commercial machine.

47. The steckerboard was in effect a plugboard at the front of the Enigma machine which had twenty-six sockets, one for each letter of the alphabet. By the 1930s, ten pairs of letters were pugged together adding 150.7 million, million additional possible configurations to the machine.

48. TNA HW 62/21, 62/20, (previously called Q/2000).

49. TNA N.I-XV – GC&CS Naval Sigint History, Vols. I–IV (previously Documents Relating to Naval Section, 1915-1939, No. 21, 16.11.27).

50. TNA HW 62/19 (previously called Q/2000, paper dated ‘End of 1927’, para. 4).

51. TNA HW 62/19 (previously called Q/2000, 29.4.32).

52. TNA HW 62/10 (previously called Q/2062, 21.6.32).

53. TNA N.I-XV – GC&CS Naval Sigint History, Vols. I–IV (Naval Special Intelligence, 1.10.32, also NID Vol. 26, 9.12.36).

54. TNA HW 62/19 (previously called Q/2064, 21.6.32, 7.11.34).

55. TNA HW 62/21 (previously called Q/2020, 11.1.38).

56. A series of figures or letters (or a group or single unit of such) which is added non-carrying figure by figure or letter by letter to the figures or letters of code groups in the process of re-enciphering or to the letters of plain language in the process of enciphering, and subtracted from the cipher in the processes of stripping and deciphering.

57. TNA HW 62/21 (previously called NID 00714/39 (Q/2000. 30.6.39)).

58. TNA HW 62/21 (previously called Q/2000, 1.7.38).

59. TNA HW 62/20 (previously called Q/2000, 20.11.36).

60. TNA HW 62/21 (previously called Q/2000, 17.7.39).

61. TNA N.I-XV – GC&CS Naval Sigint History, Vols. I–IV (previously Documents relating to Naval Section, 1915–1939, No. 1, pp. 8).

62. TNA N.I-XV – GC&CS Naval Sigint History, Vols. I–IV (previously Documents relating to Naval Section, 1915–1939, No. 65, 17.10.38).

63. TNA HW 62/21 (previously Q/2064, 14.2.38, W.F. Clarke to AGD in a covering letter enclosing letter from one of his staff, Lieutenant Commander M.G. Saunders).

64. TNA HW 62/10 (previously Q/2064, 28.4.38, pp. 13, 15).

65. DENN 1/4.

66. E.R.P. Vincent, unpublished memoirs, pp. 77–8.

67. Peter Twinn was the first mathematician to be recruited by GC&CS between the wars and arguably, was the first person in Britain to break a message encrypted by an Enigma machine which included a plugboard.

68. BP had been bought by Sir Herbert Leon, a wealthy London stockbroker and his second wife Fanny around 1882, along with 581 acres of land. They had added servants’ and domestic quarters and further extensions. The mansion was described by one former GC&CS employee as ghastly and another as indescribably ugly. Apparently, the Leons travelled abroad extensively, would see some architectural feature which they liked and would return home with a sketch of it for their builders to implement. Sir Herbert died in 1926 and his wife carried on running the estate until her death in January 1937. Sir Herbert’s heir, his son, George, duly sold off the bulk of the estate at auction by splitting it into lots. Lot 1, which initially didn’t sell and consisted of 55 acres including the mansion, stable yard and lake, was bought by a consortium of local builders and developers headed by Captain Herbert Faulkner.

69. Property transfer documents from Land Registry (Leicester Office), Bletchley Park, Title no. BM677; Sinclair’s will, 4 Nov. 1938.

70. HW 3/83 (Josh Cooper Reminiscences, written in 1975).

71. The Munich Agreement was a settlement reached by Germany, Great Britain, France, and Italy that permitted German annexation of the Sudetenland in western Czechoslovakia.

72. Conduct of Work No. 46, 15.11.39. ‘Army Interception History, Chapter II, pp. 1–3’.

73. See Kahn.

74. System by which the starting position of the Enigma machine is encrypted or concealed before being sent to recipients of specific encrypted messages.

75. The Reichswehr was the German Army from 1919 until 1936, when it was renamed the Wehrmacht.

76. TNA HW 25/12.

77. Ibid.

78. Ibid. See also Foss, ‘Reminiscences on Enigma’ in Erskine and Smith, p. 45. Foss joined GC&CS in 1924 and was tasked with examining an Enigma machine in 1927 by Travis.

79. Knox memo, 13 January, 1939, TNA HW 25/12.

80. ‘The breaking up of the German cipher machine “ENIGMA” by the cryptological section in the 2nd Department of the General Staff of the Polish Armed Forces’, S.A. Mayer, memo, 31 May, 1974, TNA HW 25/12.

81. DNI at this time was Rear Admiral John Godfrey. A number of authors who wrote about this meeting years later, mistakenly believed that it was not Sandwith who attended the meeting, but the future head of MI6 Stewart Menzies, in disguise as a distinguished British professor.

82. The ring around each Enigma wheel had 1–26 (Army/Air Force) or A–Z (Navy) embossed on it and could be set to any one of twenty-six positions. Thus there were 26 x 26 x 26 = 17,576 possible ring settings.

83. TNA HW 25/12.

84. See Rejewski, ‘How Polish Mathematicians Deciphered the Enigma’.

85. TNA HW 25/12.

86. The task was assigned to a team led by John Jeffreys and a machine was built to punch out the holes. It was a monumental task and apparently a small party was held to celebrate the punching of the two-millionth hole. The Poles were doing the same work by hand with razor blades! The Zygalski sheet method was called the Netz method (or just Netz) at BP and because Jeffreys led the work, some authors have subsequently confused the Netz with another perforated-sheet method which he developed. The Jeffreys sheet method was actually a catalogue of the effect of two wheels and the reflector. The Netz method was reinvented by Gordon Welchman in his early days at BP.

87. The German military ciphers adopted a new indication system on 15 September 1938 which the Poles attacked with their bomba machines. The reference to Mrs B.B., who has never been identified, refers to Knox’s failure to deduce the wiring to the entry disc. In (c) ‘machine’ probably refers to the bomba, SSD to Sicherheitsdientst (the intelligence service of the Nazi party), and O.S. & n.s. to old and new indicating systems used before and after 15 September 1938. Knox’s reference to Polish failure (d) is harsh as the Poles were working with limited manpower and resources. This was stretched further when the German Enigma operators were given two additional wheels, thus increasing the number of wheel configurations from six to sixty.

88. Up until May 1940, the sending operator would choose a message setting and encrypt it twice with the daily setting of his machine. The resulting six encrypted characters would appear as the first six characters in the body of the encrypted message.

89. AGD is probably referring here to Dunderdale.

Chapter 4: Bletchley Park

1. TNA HW 3/1.

2. Foreign Office 366/1059.

3. Due to a shortage of office space at BP, Elmers School, a private school for boys located nearby, had been acquired for the Commercial and Diplomatic Sections.

4. TNA HW 14/1.

5. Knox to AGD 29 September 1939, TNA HW 14/1.

6. Welchman was asked by Knox to analyse Call Signs and Discriminants. The former revealed the designation of the sender and intended recipient of the message; the latter revealed the designation of the specific Enigma setting or key that had been used to encrypt the message. See Welchman and Greenberg.

7. Enigma settings were known as ‘keys’ at BP.

8. See Welchman.

9. TNA HW 14/7.

10. Official History of MI6, p. 329.

11. Major General Sir Stewart Menzies served as head of SIS/MI6 until 1952. He died on 28 May 1968 at the age of 78.

12. TNA HW 14/2.

13. No copy of Welchman’s original proposal to Travis has survived but he documented it again in his own book and other writings. See Welchman, and Greenberg.

14. See Greenberg.

15. TNA HW 3/107.

16. TNA HW 14/3.

17. Ibid.

18. Ibid.

19. The ‘Phoney War’ was the name given to the period of time in WW2 from September 1939 to April 1940 when, after the blitzkrieg attack on Poland in September 1939, there was little military engagement between opposing forces in Europe. The term ‘Phoney War’ was first used, allegedly, by an American senator called Borah. Winston Churchill referred to the same period as the ‘Twilight War’ while the Germans referred to it as ‘Sitzkrieg’ – ‘sitting war’.

20. Admiralty Hydro and Ultra series, 5.1.40–2.7.40.

21. See Chapter 3, Note 78.

22. A Watch was like a shift in the modern workplace.

23. SIS Communications was known as MI6 Section VIII and was based at Whaddon Hall in the village of Whaddon during WW2.

24. TNA HW 3/33.

25. IV LN Versuchs or Luftnachrichtenversuchsregiment.

26. TNA HW 62/21 (previously called Q/2006, 29.9.40).

27. TNA HW 62/21 (previously called Q/3261, 29.12.39).

28. TNA HW 62/21 (previously called Q/2006, 28.5.40).

29. GC&CS Naval Sigint History, Vol. IV, pp. 29–41. Also see Batey.

30. The Foreign Office officials were Miss Emily Anderson, who would later work at Berkeley Street, and her chaperone.

31. TNA HW 62/21 (previously called Q/2006, 22.7.40).

32. TNA HW 62/21 (previously called Q/2065 13.11.40).

33. Q/3213, 1.2.42.

34. Q/2006, 20.5.41.

35. TNA HW 62/21 (previously called Q/2022, 11.4.40).

36. TNA HW 62/21 (previously called Q/2006, 6.10.40).

37. The French party included: Capt. Roger Baudouin, at BP 12 June 1940 to 9 March 1942 then Liaison Officer between Free French Sigint and BP. Died in April 1944 in an aircraft accident while en route to Algiers (by then a Commandant). Wartime pseudonym R. Baldwin; Capt. Bracquerie (believed to have returned to France at some point after the Armistice); Lt. Graverand (returned to France after the Royal Navy attack on the French Fleet at Mers-el-Kébir); Capt. Hutter (believed to have returned to France after the Armistice); Kiefe (believed to have joined the Free French in London summer 1940); Capt. Felix Meslin (at BP 27 April 1940 – 9 March 1942, then Wavendon, then London. Wartime pseudonym F, Miller); Lt. André Mirambel (at BP 27 April 1940 – 9 March 1942, then Wavendon, then London. Wartime pseudonym M.M. Merry); De la Pierre (returned to France after the Royal Navy attack on the French Fleet at Mers-el-Kébir); Roger (Believed to have joined the Free French in London summer 1940); Lt. Jean Emile Royer (arrested in Nov 1940 for a major security breach – no further information. Interned. ‘C’ ruled in September 1944 that he was not to be expelled to France until after VE Day); Lt. Claude Schaeffer (at BP 1940. Officially joined the Free French Naval Force in London. At BP 27 April 1940 – 9 March 1942, then Wavendon, then London. Brought his whole family to the UK so no pseudonym); Lt. Marc Vey (at BP 27 April 1940 – 9 March 1942, then Wavendon, then London. In 1944 replaced Baudouin as Free French liaison with BP. Wartime pseudonym M.A. Volney).

38. Government Code and Cypher School Report for 1940, TNA HW 14/11.

39. TNA HW 14/9.

40. Q/412, 23.11.40.

41. Q/412, 25.11.40.

42. Q/312, 24.11.40.

43. TNA HW 62/21 (previously called Q/2068, 13.12.41).

44. TNA HW 62/21 (previously called Q/2068, 14.2.41).

45. TNA HW 62/21 (previously called Q/2006, 25.2.41).

45. TNA HW 62/21 (previously called Q/2067, 17.3.41).

47. TNA HW 62/21 (previously called Q/2067, 18.11.41).

48. Sixta History, Section A, p. 16.

49. Q/3175, 5.2.41.

50. Q/3648, 8.2.41.

51. Q/516, 20.4.41.

52. History of I.E. (Intelligence Exchange), pp. 1–2.

53. N.S. Misc., 21.4.41.

54. Allied Sigint – Policy and Organisation, Chapter III, Part 1, pp. 84–5, TNA HW 43/75.

55. N.S. Misc., 8.3.41.

56. History of I.E., p. 8.

57. See Smith and Erskine.

58. TNA HW 62/21 (previously called Q/2006, 31.8.40).

59. People working on calculating machines were known as ‘computers’.

60. A network of observing stations had been set up covering Europe and the rest of the world. At certain agreed hours the observers at all stations made a note of the weather and incorporated it into a numerical international code message. This was typically of the form IIICLCMwwVhNhDDFWN, where III was the number assigned to the observing station; CL and CM were the types of low and medium cloud; ww was a 2-figure number describing the weather at the time of observation, from ‘00’ which meant cloudless to ‘99’ which meant heavy thunderstorm with hail; and so on for the other meteorological elements. This taken from an Autobiographical Sketch prepared by G.C. McVittie for the Royal Society of Edinburgh during 1976/77.

61. Interview in April 1983. See Cave Brown’s book on Menzies.

62. TNA HW 14/22.

63. Hugh Alexander, who became head of Hut 8 and remained in GCHQ after the war, wrote to the Director of GCHQ, Sir Clive Loehnis, in 1963. Margaret Rock had left GCHQ in 1963. She ‘bequeathed’ Hugh Alexander, as he went on to say in a covering note, ‘a fascinating series of memoranda from Dilly Knox written about 1940-41. Dilly was head of the original Enigma party and I suppose the senior cryptanalyst at the time. I enclose for your interest a letter written to the then Director [Menzies] … just so that you can appreciate how well behaved we analysts are nowadays!’ Loehnis’ reply: ‘and you of course can appreciate the advantages obtained from working with an enlightened and sympathetic Directorate’.

64. Jim Beach, ‘Origins of the Special Intelligence Relationship? Anglo-American Intelligence Co-operation on the Western Front, 1917-18’, Intelligence and National Security, Vol. 22, No. 2 (April 2007), pp. 229–49.

65. This involved talks about supply and defence programmes and staff plans. Churchill and Roosevelt had agreed in principle to the pooling of information on these subjects.

66. See Hinsley, Vol. 1, pp. 312–13.

67. Henry Stimson diary, 23–24 October 1940, Yale.

68. In an interview after the war, Sinkov said that the officer who greeted them was John Tiltman. In Currier’s account of the trip to England, he thought the officer was Humphrey Sandwith.

69. Accounts by Currier (Prescott Currier, ‘My ‘Purple’ Trip to England in 1941’, Cryptologia, Vol. 20, Issue 3, (1996), pp. 193–201) and by the head of OP-20-G, Commander Laurance F. Safford (L.F. Safford, in Dundas P. Tucker, ‘Rhapsody in Purple: A New History of Pearl Harbour – Part I’ (Greg Mellen (ed.), Cryptologia, Vol. 6 (1982), p. 216) claimed that the Americans brought two machines with them. Ralph Erskine has argued that based on the weight of the items shipped to Britain, only one machine could have been included (Ralph Erskine, ‘From the Archives. What the Sinkov Mission Brought to Bletchley Park’, Cryptologia, Vol. 27, Issue 3 (2003), pp. 111–18).

70. TNA HW 62/21 (previously called Q/2049, 6.5.43, AZ/393.

71. According to GCHQ, the Roll of Honour in a wood and glass cabinet now stands on the spot where the sherry cask was placed.

72. Sinkov and his group were shown the Bombe machines as their names appear in the Hut 11 Visitor Book, held today in the BP Archive. Apparently this was done with the express approval of Churchill.

73. Ralph Erskine, ‘What did the Sinkov Mission Receive from Bletchley Park?’, Cryptologia, Vol. 24, Issue 2 (2000), pp. 97–109.

74. TNA HW 14/45. AGD’s made it clear that his visit to Ottawa would only take place if he could avoid meeting Herbert Yardley, a former US cryptanalyst now working in Canada.

75. Denniston Report, TNA HW 14/45. See also Burke.

76. Pearson to Massey, 23 Sept. 1942, CSE doc. 000221-22.

77. Rowlett was the first of William Friedman’s original employees, hired for the Army’s Signal Intelligence Service (SIS) in 1930. From 1939–40, he had played a major role in solving a much more sophisticated Japanese diplomatic cipher machine, nicknamed ‘Purple’ by the US. Friedman and Rowlett also had crucial roles in protecting American communications during WW2. Working with the US Navy, they helped design the SIGABA, the cipher machine which was never solved by the Germans during the war. After the war, Rowlett eventually served in a number of senior roles in both the NSA and CIA.

78. TNA HW 14/45 ‘Notes on Conference Held August 14/15, 1941’.

79. United States Navy File of Correspondence with Department of State, 1919-1950, SRH-281, CCH Holdings, 74.

80. TNA HW 14/45 ‘Interrupted Conference with Commander Safford’, 18 August 1941.

81. Agnes May Meyer was born on 24 July 1889. She graduated from Ohio State University in 1911 and on 22 June 1918, she enlisted in the US Naval Reserve. After initially being assigned to the Office of the Chief Cable Censor, she on 18 June 1919 she moved to the Code & Signal Section with Naval Communications. After leaving the Navy, she was reemployed as a civilian and worked within MI-8, the ‘American Black Chamber’. She learned her trade at Riverbank Laboratories, where Willian Friedman had trained. In 1924 she joined the Research Desk of the Navy’s cryptographic section, OP-20-G. She married Michael Bernard Driscoll on 12 August 1925 and after WW2, she worked within the NSA until her retirement on 31 July 1959 at the age of 70. She died on 16 September 1971.

82. TNA HW 14/45 ‘Interrupted Conference with Commander Safford’, 18 August 1941, Para. 6.

83. Safford was informed that as soon as Driscoll’s work proved ‘in any way successful’ that GC&CS wanted to send out one of its best men. TNA HW14/45 ‘To Washington December 1 1941, ‘Your CXG 105 of 27.11.41’.

84. It seems that the Germans also considered a catalogue method. TICOM-I-38 – Report on Interrogation of Lt. Frowein of OKM/4 SKL III, On His Work on the Security of the German Naval Four-Wheel Enigma, June 21, 1945. Frowein had been assigned to check the security of the naval system in the summer of 1944 after the German naval authorities discovered a suspicious pattern of U-boat sinkings. In his interview with Allied investigators, he claimed that he had found a method to read the four-wheel Enigma using rather traditional methods of determining the fast-wheel, then, using a large catalogue of the other possible settings of a machine. As a result, the Germans ordered that only double turnover wheels be used in the fast position because his method would not work with a multiple turnover wheel in the fast position. However, his method demanded a very long crib, an enormous catalogue (some 4,000,000) entries and forbidding amounts of human and tabulator time if it was to be turned into more than a theoretical exploration.

85. National Archives of Canada (Ottawa), RG24, 12,324,s.4/cipher/4D.

86. Col. D.A. Butler (mI8) to DDMI(O), 27 December 1939 as above regarding remarks by AGD.

87. AGD memo of May 1943 in Virginia Military Institute, William Friedman papers, 110, SRH-153.

88. TNA HW 14/45 ‘Dispatch of Packages for US Authorities at Washington’, 28 August 1941.

89. TNA 14/45 ‘Dear Eddie’, 9 October, 1941.

90. Turing deduced that even if the wheel order and ring settings were known, it would take 72,800 hours of work to find a solution; National Archives and Records Administration (Washington), RG38 CHSG, Library, Box 104.

91. TNA HW 14/48, GC&CS memorandum of 16 August 1942.

92. TNA HW 14/74.

93. TNA HW 14/14.

94. TNA HW 14/16.

95. TNA HW 14/20.

96. Ibid.

97. TNA HW 8/23.

98. TNA HW 62/21 (previously called Q2006, 4.4.41).

99. TNA HW 62/21 (previously called Q2006, 7.11.41).

100. Allied Sigint – Policy and Organisation, Chapter III, pp. 109–10.

101. BP’s output was known as Most Secret Source and later, ULTRA.

102. TNA HW 62/21 (previously called Q/2006, 10.9.41).

103. The Typex machine was developed initially for the Air Ministry and following successful trails, 350 machines were ordered in June 1938, of which thirty went for trials with the Army. By October 1939, the War Office had ordered 207 machines while the Admiralty had ordered 630, of which around 350 were intended for use on ships. There was a shortage of machines throughout the war, given slow production. The total cumulative production of the two main models, Mk. II and Mk. VI was 500 by June 1940, 2,400 by the end of 1942, 4,000 by December 1943 and 5,500 by May 1944. The total built by the end of the war was around 12,000.

104. Q/3647A, 23.12.41.

105. Q2073, 19.1.42, Q/2065, 5.1.42.

106. Both the letter and Churchill’s minute appear in Hinsley, Vol. 2, Appendix 3, pp. 655–7. A facsimile of Churchill’s minute appears on p. xiii of Erskine and Smith. The letter and minute are in TNA HW 1/155. They are Crown copyright and are reproduced with the permission of the Controller of Her Majesty’s Stationery Office.

107. P. S. Milner-Barry, ‘“Action This Day”: The Letter from Bletchley Park Cryptanalysts to the Prime Minister, 21 October 1941’, Intelligence and National Security, 1 (1986), pp. 272–3.

108. Hinsley, Vol.2, p. 657.

109. Ibid., p. 26.

110. All were sent to the Foreign Office, the Admiralty – 4,526,; the War Office – 3,767; the Air Ministry – 4,212; MI5 – 1,166; MEW – 3,639; nine other departments and authorities received a smaller selection.

111. Kimball, Roosevelt and Churchill, Vol. 1, item C-32/1: letter from WSC to FDR, dated February 25, 1942

112. TNA HW 3/33.

113. Q/2022, 20.2.41.

114. TNA HW 62/20 (previously called Q/2000, 11.3.38).

115. NID Vol. 21, 1.3.47.

116. TNA HW 62/20 (previously called Q/2000, 18.6.36).

117. TNA HW 62/21 (previously called Q/2006. 23.1.42).

118. TNA HW 62/21 (previously called Q/2006, 10.9.41).

119. TNA HW 62/21 (previously called Q/2006, 9.9.41).

120. TNA HW 62/21 (previously called Q/2068, 24.9.41).

121. Allied Sigint – Policy and Organisation, Chapter III, p. 120.

122. TNA HW 62/21 (previously called Q2006, 1.4.41).

123. TNA HW 62/21 (previously called Q/2006, 30.1.42).

124. Ibid.

125. TNA HW 62/21 (previously called Q/2006, 4.2.42).

126. Head of ISOS and then combined ISOS and ISK from March 1944.

127. Head of Diplomatic Section until the move to Berkeley Street.

128. Responsible for communication lines and all GPO liaison with GG&CS.

129. TNA HW 14/27.

130. TNA HW 62/21 (previously called Q/2068, 6.2.42).

131. Welchman later told Robin Denniston that he had good reason to feel that his father was badly treated: ‘It was utterly disgusting – far, far worse than the way I was treated, which was bad enough.’ See Greenberg.

132. See Greenberg.

133. See Smith.

134. Paper written for Robin and ‘Y’ Denniston by Filby on 15 April 1981. He also made the point in a letter to Ronald Lewin on 11 April 1979.

135. Travis was formally appointed Director of GC&CS in March 1944 and knighted in June of the same year. GC&CS was renamed GCHQ and Travis remained as its director until 15 April 1952.

Chapter 5: Berkeley street

1. Filby letter to Robin Denniston, 15 April 1981.

2. Kennedy’s diaries are held by the library of the University of Sheffield. See Ferris.

3. Filby letter to Robin Denniston, 15 April 1981.

4. Kullback was recruited to SIS, based in Washington in 1930. He was responsible for breaking many Japanese codes, ciphers and machine systems during WW2. After the war he became Chief of the Research and Development effort at the NSA, retiring in 1962. See Oral History Interview with Kullback, NSA OH-17-82.

5. Sandwith attended the Pyry conference with AGD and Knox in Poland in July 1939.

6. Discussion paper presented by Captain H.R. Sandwith, 6 April 1942, NAC, RG24, 3806, NSS-1008-75-20. This is a rare contemporary description of British Sigint.

7. Little to Denniston, 18 April 1942, Canadian Security Establishment (Ottawa) doc. 300.

8. Shortly after returning from Britain, Little was promoted to lieutenant commander and appointed Director of Naval Intelligence.

9. AGD to Little with list attached, 6 June 1942, NAC, RG24, 8125, NSS-1282-85(1).

10. In this system, the code groups were enciphered by additives in the usual way, but the resulting superenciphered groups were then enciphered a second time using additives from the same book, but with a different starting point. This method enabled the additive book to produce several million ‘double additives’. (A complete book of Floradora additives covered a range from 0000 to 9999 (page 00, row 00 to page 99, row 99, with six groups of five additives in a row). The first half of a book (pages 00 to 49) was used for encipherment, while the second half (pages 50 to 99) covered decipherment. The second part consisted of the digital compliments of the first half (so that additive group 43642 in the first half would be 67468 in the same relative place in the second), to allow addition rather than subtraction to be used when deciphering messages. Unusually, addition was chosen for both operations because it gave rise to fewer errors by the cipher clerks.)

11. ‘Report of Cryptographic Mission 0 Maj. Sinkov 1941’, 8-10 (HCC, Box 1296, Nr. 3873). GC&CS Report, 1940, German diplomatic section, TNA HW 14/11.

12. Head of the German Diplomatic Section from 1939 to 1942 when she left due to ill health.

13. GC&CS (civil section), ‘Report on present position of legibility of foreign ciphers’, 25 May 1942, TNA HW 14/38.

14. German diplomatic section minute, 8 August 1942, TNA HW 14/48; AGD memo of 31 October 1942, para 24 TNA HW 14/45; AGD to Tiltman, minute of 8 March 1942, item 7, TNA HW 14/4. According to Filby: ‘Denniston received a message from the British Consul in Lourenco Marques, the capital of Portuguese Mozambique on the east coast of Africa. The German Consul’s primary job was to report shipping passing the port. Denniston received a letter and a pouch. “Dear Alastair”, the message read, “this was dropped in my letter box by a sailor, thinking it was the German Consulate. Are the contents of any use to you?” Remarkably, they contained the daily keys for the next three months which enabled the section to work out the additive lines used in every message sent by the German Foreign Office. With the help of SIS at Arlington Hall, the system was effectively broken. The main break was based on a message from Berlin to Dublin that said that new instructions for the use of ‘Floradora’ between Berlin and Dublin were being sent in a message which would be like an OTP message. The new ‘Floradora’ system would then become the principal form of communication between the two centres. Further information about the operation of the system gave the Section all it needed to break ‘Floradora’.