In May after the birth of my first child Andrew Peter I reported in my ill-fitting gunner’s battledress to Colonel Stratton at No 3 Caxton Street, but was told by him that he was expecting a Lieutenant Webster and that I had better go out and buy myself a uniform. So I did and pranced through the streets with my swagger cane, though in fact he was wrong. I was not gazetted for another two weeks. This was not quite fair on the other two recruits, who were to be gazetted about the same time but for some reason had not been told to put up a pip at once. These two were Chris Wills and Hamish Blair Cunynghame, who were to work close to me for much of the war. Soon, however, we were all three second lieutenants and formed a unit assisted by a sergeant and a rogue of a corporal acting as a clerk.
I was the oldest and started out as head of the unit, but I could not manage the rogue corporal and relinquished the headship to the tall dynamic Hamish, who was good at bullying and cajoling difficult and stupid people.
We had not, I soon realized, joined the cryptographers but number 6 Intelligence School, which was being set up by MI8 to study the enemy communications systems. Our primary task, we were given to understand by Stratton, was to break the call sign system used by the German air force. However Stratton’s explanation both of this task and of the organisation to accomplish it, was pretty vague and inadequate. A tubby little professor of astronomy, he longed to be back in his observatory and his heart was not in wireless intelligence. So we had to take our own bearings and only gradually did we begin to understand the complexities.
What was immediately apparent was that our floor was inhabited by some two dozen civilian women of very Mayfair style, who spent their time recording on punched cards the call signs and frequencies used by the German armed forces. These women, I discovered, had been recruited in rather a strange way. A certain Captain Bolitho had made something of a name for himself in wireless intelligence by inventing a device for ‘finger printing’ the bleeps of transmitters. Somehow he got the War Office to agree to his recruiting his own band of bright, well-connected women and using them on top secret work. Mary, the first he recruited, described to me how it happened. Her sister was at a wedding early in 1940, when a man asked if she wanted a job. She didn’t, she had one. ‘Pity! My brother wants a smart girl’. But when she got home, she told Mary and after various ringings up, a man’s voice came on the phone.
‘Are you Mary?’ ‘Yes’
‘Do you want a job?’ ‘Yes’
‘Meet me outside the Ritz at 6.30’ ‘How shall I know you?’ ‘I’m six foot five!’ So Mary went and got the job. Later she brought a friend for Bolitho to look at. He did just that, he sat silently looking at the girls and sucking his pipe.
Finally Mary burst out laughing.
‘Well, does she get the job?
‘Of course she gets the job. Come and have a glass of champagne’.
Mary told this like something out of Evelyn Waugh, but in fact Bolitho’s recruitment methods were highly successful. He got a marvellous bunch. Later we recruited direct from the universities and used intelligence and aptitude test but these later recruits were not on average up to ‘Bolitho’s Angels’. He was probably checking up through the social network, which at this level tends to be franker and more demanding than teachers and employers. Three of his recruits in particular - Judith Whitfield, Elizabeth Roscoe and Iva Dundas - were to become key personnel, vital to the organisation of our work.
Bolitho did not pay his recruits out of his own pocket, though he did buy the punched card machines and other office equipment. The women he simply told that if they were prepared to start working for nothing, the government would be paying them within three months. He was right. By the time I arrived, they were all civil servants. Bolitho himself was not now working with this part of the organisation. But he was living in the St Ermins Hotel, which formed part of the same block as number 3 Caxton Street and was connected to it by a passage. His huge, loose figure would appear sometimes at night, when we had to keep some kind of watch. And if there was nothing on, he might invite some of us to his flat in the St Ermins to see ‘some pictures of cows’, i.e. films of his Argentinian hacienda.
By day Bolitho would visit the office and wander around, prodding the punched card machine and other office equipment and furniture and saying ‘Do you know whose these are? They’re mine and I haven’t been paid for them’.
Pretty soon however, all this was settled and we then saw little more of this kindly and surprising man, who lent me his car when my wife came up to London for a brief spree and who maintained the little flower bed under the Admiralty Arch, which I had always thought was publicly maintained.
Besides our unit and Bolitho’s angels there was on our floor a Captain Wishart, a statistician, who was presumably supposed to organise research into the German system of call sign allocation, while on the floor above there were other officers including Major Tozer and Lieutenant (soon Captain) Crankshaw. We did not at first know the nature of the upstairs work, but were later told that they were studying the German armed forces radio network in the light of decodes of German messages. We also came to know that a party under Captain Lithgow was doing similar work at a mysterious place known variously as Station X, BP, Bletchley Park or Bletchley, where the German ciphers, including the machine cipher called Enigma, were broken. It was impressed on us that Bletchley’s cryptographic success was a secret of the highest importance, which the civilians and other ranks on our floor were not supposed to share.
The upstairs party was soon joined by a new recruit - Freddie Edwards. Freddie was a tall powerfully built young blond, whose eyesight was so bad that everything more than two feet away was a blur and he could read only by holding a book opposite his ear and reading out of the corner of his eye. So he had been graded very logically as unfit for active service and put in the pioneer corps to dig trenches. What had not been taken into account, was that he had been a boy chess champion and had learned to read from chess textbooks and that his German was pretty good.
Freddie had heard that there was some sort of interesting place at number 3 Caxton Street. So he went there carrying a plain official envelope marked ‘Captain Smith, to be delivered personally’. Fortune was with him. The answer came back. ‘Captain Smith is out, but Major Tozer will see you’. After talking to Freddie, Tozer said, ‘The body stays. The transfer comes through later’. I think Freddie came originally as a private, but he was soon a sergeant and ended the war as a captain.
In the meantime Hamish, Chris and I had set about trying to help solve the German call sign system from the sources available to us. To understand what these were requires some explanation both of the German armed forces’ systems of radio communication and of the procedures and records used at the British intercept stations eavesdropping on them.
The radio communications of the German armed forces were on a huge scale and, to avoid confusion, were based on the star system, whereby all communication was to, from or through the control of the ‘star’. Control had no call sign. It called an outstation by using the same call sign, which that outstation used to call control. Usually each star was allocated one or two frequencies and these frequencies would stay the same for long periods. The frequency was thus an important factor in identifying a ‘star’ picked up by our interceptors, and my memory for numbers proved useful; but it was seldom enough in itself for reliable identification of the ‘star’ and did not identify the individual station. Call signs of course existed to do just that if the system of call sign allocation was known. But the call signs, which consisted of three symbols (either letters or numbers), changed daily according to a system, which we had not solved.
The communications between the stations on the German ‘stars’ were in Morse code and consisted of message transmissions, most of which were in cipher or code (usually machine cipher from regiment or staffel upwards), and operators chat (keying, calling, notice and receipt of messages, queries, checks, cancellations etc.) which was mainly in the international Q code used for brevity, not security, by most Morse senders throughout the world. The British operators monitoring these communications at the intercept stations set up for this purpose at Chatham (later moved to Woodhouse near Loughborough), Chicksands, Harpenden, and elsewhere, had to hunt around the frequency bands to find transmissions of the German armed forces or to listen on frequencies where they expected to find particular ‘stars’; and to make two types of record of what they heard. First of all, they had to write down every message on a message pad and, as soon as it was completed, hand it over for despatch to the cryptographers at Bletchley. Secondly they had to record all operators chat and the preambles of messages in a log or, as the Americans called it perhaps more aptly, a chatter sheet. The logs were handed over to intelligence officers at the intercept station who compiled from them a daily report of the frequencies and call signs of the ‘stars’ heard. These reports were sent to 3 Caxton Street (among other places) and formed the basis of the attempted analysis of the call sign system.
The call-sign book used by the German army had been captured. It contained 40,000 three-symbol call signs arranged in 200 columns by 200 rows. Military stars were allocated a column for the day, while their stations were each allocated one or more rows, which they kept while the column changed daily. The system of column allocation had not yet been solved but it was believed to be some kind of grid applied to a reordering of the columns.
Interest in the German Army’s communications, however, was low in the summer of 1940. The fighting in Europe was over. The Battle of Britain was on. The air force call-sign system was the thing. We suspected that it was similar to the army system, but the evidence was confusing and conflicting. We changed from punched card recording to manual indexing, which we thought might throw up leads during the actual process of writing on the card. Elizabeth Roscoe and I compiled a large chart, which should have shown the reappearance together of call signs from the same column of the supposed call sign book. But the evidence was inconclusive and we gave up.
I was, I think, chicken-hearted. There was some positive evidence and the inconsistencies were due to the unreliability of the material. The intercept operators were brilliant at finding German air force traffic and picking out the ‘stars’ they were meant to be covering but even so they tended to pick up and confuse call signs of separate stars on neighbouring frequencies and to make errors in recording transmissions difficult to hear, while the recorded frequencies for the same star might for a variety of reasons vary from day to day. The intelligence officers at the intercept stations, whose primary concern was to see that they gave Bletchley the messages it wanted, had little time to sort out these matters when making their daily reports.
One reason for my giving up so easily was that we had begun to adopt a new short-term approach to the problem of star and station recognition. We were now receiving some of the actual logs from the intercept stations. And we had begun to set some of the staff to ‘log reading’ i.e. to summarising from the logs the pattern of communication of a ‘star’ by means of a diagram with arrows showing the direction of messages, a list of message preambles and notes of significant chat. These summaries, it was found, made it possible to recognise stars and some of the stations on them from day to day even without knowing the call sign system. Crankshaw was fascinated by the diagrams. For when taken together with the addresses, signatures and operating instructions supplied to him from the decodes they helped him to build up a picture in depth of the German air force chain of communication, which was in effect the chain of command, i.e. the order of battle. Elizabeth Roscoe, who was nearly always right, pointed out that the improved identifications provided by log reading might make it easier to reconstruct the call sign system, but by that time I was more interested in short-term results.
The effort put into log reading was accordingly increased. New staff, largely ATS, were recruited and the log reading party was moved out of the London blitz to the Warren, a large house at Harpenden and put under the command of Crankshaw, now a captain. A small party was left behind in London to try to work out the air force call sign system, which they did successfully about two years later. A little earlier Malcolm Spooner working on his own at the intercept station at Beaumanor solved the similar system by which the German army allocated the columns from their similar but separate call sign book. Eventually a copy of the actual call sign book used by the German air force was captured and almost at the same time the Russians gave us a second captured copy.