Chapter Eight

They Gathered around like Family

By the late 1940s, it was a relationship that had become unprecedentedly intimate; and it was striking to consider that this closeness had been sparked in circumstances that were almost picturesque, if not downright romantic: that snowy January midnight in 1941 when four senior US cryptologists had arrived, in the thick darkness of the blackout, at the front door of Bletchley Park. These Americans had brought with them a technological marvel: the machine they had constructed to combat the Japanese cypher system. Bletchley’s director Alastair Denniston offered his guests sherry in the quiet book-lined study that was his office. Given that at the time America was still pretty much one year away from joining the war, this initial meeting of minds was truly remarkable; doubly so given the inevitable rivalry between the two nations. After the war, there had been some in Washington DC who wanted to see this continuing romance between the two nation’s codebreakers cooled down. Yet – even aside from the triumph of Venona – the relationship continued to be irresistibly fruitful.

For instance, in 1946, the British and Americans had started working together on cracking Soviet traffic under the name ‘Operation Bourbon’, later renamed ‘Rattan’. This success was followed by an operation named ‘Caviar’, in which inroads were made against a Soviet teleprinter system.

After this came what was called the ‘Poet’ operation. The Soviet armed forces’ machine cyphers were broken by a team at Eastcote, and the system of doing so was christened ‘Coleridge’. According to intelligence historian Michael Smith, the equipment being used by the Russians in this instance bore a useful similarity to the ‘Hagelin’ electric encryption machines used by the Swedes. This was one of the moments when the American liaison officers working in London looked at the British – or more specifically, in this case, at Hugh Alexander, who had headed up the ‘Coleridge’ assault – and understood the depth of brilliance that they were working with. According to a communication sent back to Washington in the spring of 1947, Alexander’s ‘Coleridge’ codebreak – which opened a window into a world of Soviet administration, which in turn yielded invaluable intelligence about military numbers and priorities – was ‘the most important, high-level system from which current intelligence may be produced and is so in fact regarded here’.1

One of the Americans working at Eastcote who joined in with the Poet operation – branching off into another decryption project, ‘Longfellow’ – was a wonderfully engaging mathematician whose name is now venerated by UFO conspiracy theorists the world over. Howard H Campaigne – who had worked under Professor Max Newman and who was, later in his career in America, to do so much to push computer technology along – wrote a paper in the late 1960s which came to light several years ago. Or, at least, a fragment of the paper surfaced. It was about coded messages from a most unusual source. ‘Recently a series of radio messages was heard coming from outer space,’ Campaigne wrote in an enjoyably deadpan – even mischievous – introduction. The fragment of his paper does not indicate whether these messages are set as a hypothetical test by himself or not, but the way he frames the effort to decode the messages, broken into fragments, suggests a sly attention-grabbing way into a mathematical riddle as opposed to an extraordinary revelation that will alter the course of human history.

In conversation with a National Security Agency colleague in the 1980s, Campaigne was happy to muse on the rather more terrestrial concerns that he had faced in his cryptography. He was quite candid about how US codebreakers had identified the need to break into Soviet cyphers some distance before the end of the war. ‘President Roosevelt had said that we were not at war with Russia and we wouldn’t study their codes. But there were people down the line who thought that was very unwise.’

But the study of Soviet messages was kept extremely low-key, for understandable reasons. ‘It was extremely modest,’ Campaigne said. ‘We did a little intercept. We had great difficulty covering up for our intercept stations. And practically all we had was a few samples of traffic.’

On top of this – and despite the unprecedentedly close relationship between the US and UK codebreakers – he also confessed that there had been some sneaky spying upon the affairs of their British friends. ‘Well, we looked a little at some of their things,’ Campaigne noted. ‘It really wasn’t an intelligence effort. It was more a cryptographic monitoring… the British were using an encyphered code for the convoy thing and we were convinced that the Germans were reading it. And we told them that and it was hard to persuade them that it was true.

‘We also got hold of a British machine,’ he continued. Professor Campaigne was referring to the Typex encyphering machine which in some ways mirrored the workings of the German Enigma. ‘And of course we took it apart and examined it with great interest… we did do some analysis of the British cypher machine without telling them. Looking for weaknesses and we didn’t uncover anything. It was a pretty secure device really.’2

In drizzly 1940s Eastcote, American fascination – and sometimes bewilderment – at British life continued. According to security expert Gordon Corera, one especially beguiling detail concerned official struggles with ramblers. Around Eastcote – and other listening stations buried rather deeper in England’s sylvan glades – there was a criss-crossing network of ancient footpaths and rights of way dating back centuries. Under the new Labour government, which viewed the rights of ordinary man as trumping those of the landed aristocracy, there were a great number of walkers who were starting to assert their rights to use them, no matter how close these footpaths may have been to secret establishments. There was nothing in America to quite match the ferocious determination of the ramblers and their expertise on the right to march along certain by-ways; by contrast, in the US, such people would be warned off forbidden land with guns.

Some footpaths in the most extraordinarily sensitive areas remained open, including one, dating all the way back to 1565, that ran between two blocks of the Eastcote establishment. Obviously there was security fencing and walls but nevertheless, the proximity to the secret work was startling. Incidentally, things are just as free and easy now for walkers: the site of so-called GCHQ Bude in Cornwall, featuring an array of satellite dishes, has the South West Coast Path running alongside it, the equivalent of a walkers’ motorway. Meanwhile, the giant golf-ball surveillance structures at Fylingdales in Yorkshire are of themselves something of a tourist attraction for ramblers. Obviously one cannot wander around the site itself, but about ten years ago the Ministry of Defence opened up tracts of the North York Moors surrounding the installation that had, for some decades, been forbidden territory to the public. In any event, many codebreakers and secret listeners were themselves keen walkers: Christopher Barnes at Beaumanor Hall in Northamptonshire relished the countryside all around; Alan Turing made a habit of running through the countryside around Hanslope Park. As it happens, that particular park is very much barred to walkers now; a most unusual defeat for the rambling community. Walking groups post complaining blogs about having to circumnavigate the estate, but there are some areas that are still deemed too clandestine to risk it.

In cultural terms, what was slightly more difficult for the Americans coming to 1940s monochrome Britain was the greatly reduced standard of living. For US cryptographers such as Joan Malone, who had been brought over to work alongside veteran British cryptographer William Bodsworth, this new world of fish paste, of processed ham, of scarce to non-existent luxury items, must have been quite an ordeal after the unthinking plenty of Virginia. This was a landscape not merely of austerity, but of rationing even more ferocious than that seen during the war. Added to this was the spectacularly biting winter of 1947: the snow came down relentlessly, never clearing. Rather unkindly, Joan Malone was given the nickname ‘Sneezy’. The unconditioned air in the Eastcote blocks, together with the unpleasantly chilly weather, left her a martyr to her nose. The summer months were not much better: leafy Eastcote, with all its surrounding parks, made her hay-fever a nightmare.

Added to this particular discomfort were the wider privations: the continual shortages of coal and fuel, combined with the coupons needed to buy any kind of new clothing. This was a time when women were forced to make themselves garments out of old blankets. Joan Malone, together with her small accompanying team of American codebreakers, had come from a burgeoning consumerist paradise, where orange juice and fresh coffee were expected, to a somnolent London suburb where such things had never been known; a suburb where everything was shut all day Sunday, and on Wednesday afternoons too. The proximity of the West End would only have been a partial consolation, since the city was still a soot-smirched parade of British Restaurants and frowsy pubs.

The pairing of Joan Malone – a formidably skilled analyst and linguist – with British codebreaker Bodsworth, himself a polyglot, in some ways symbolised the entire US–UK relationship. Here was an old-school male academic, a product of the traditional English education system, sparking with a woman who in some ways represented a future of equality, and certainly a future of growing American dominance.

A key figure in forging a strong post-war partnership with these bright Americans was Group Captain Eric Jones. At the start of his codebreaking career, Jones had attracted the attention of those from backgrounds far more genteel than his own. His intellectual trajectory, when he had been recruited from Air Ministry intelligence to Bletchley Park in 1942, was strikingly different to that of the off-the-wall academics roaming the premises. Although fiercely bright, Jones was not a university man. Indeed, he had left school at the age of 15. He joined his family’s textile firm and then left that by the age of 18, in order to start up his own business independently. A terrific success he made of it too; and it was only the urgency of war that made him hand it over to associates, aged just 33. He might not have been an Oxbridge classicist – Jones attended the King’s School in Macclesfield – but his wider experience clearly set him up fantastically well for the extraordinary life that he was to lead. At Bletchley, he had been placed in temporary charge of Hut 3 and Luftwaffe decrypts; and this, in turn, led to permanent leadership. Commander Travis had been immediately impressed not merely with Jones’s intelligence, but also by the way that he could bring a semblance of order to all the jostling, wild intellects working in that hut; an easy knack for leadership based on a charisma that many were to pay tribute to across the years.

Jones also had a gift for organising intelligence: in 1945, he had been sent to Washington DC to act as the representative of British Signals Intelligence. As in Britain, his straightforward and easy manner won him good friends – crucial to the quite extraordinary level of trust that evolved between America and Britain. Jones had both laser-beam intelligence and also a manner that was found universally pleasing. Chess champion Stuart Milner-Barry wrote of him: ‘Jones was not a scholar or an academic; I suppose he must have had some knowledge of German but primarily he was a businessman coming from… Lancashire. He was a genuinely modest man who regarded himself as having little to contribute compared with the boffins with whom he was surrounded; in fact he was a first-rate administrator who was liked and trusted by everyone.’3

Codebreaker William Millward also paid tribute to Jones’s awesome powers of diplomacy: ‘He had the qualities of principle, strength of character, and a firm grasp of essentials which enabled him to settle most of the tiresome intrigues and controversies.’4 Ralph Bennett described him as ‘firm but understanding’ meaning that everyone could concentrate on their work ‘undisturbed by internal conflict’.5

Jones’s goal in Washington was to work on cementing an intelligence liaison – and it was in large part through his efforts that America and Britain came to seal their secret codebreaking alliance, an arrangement that still holds firm today. Before then, he had worked with the US codebreaker Telford Taylor who remembered him with great fondness: ‘Group Captain Eric Jones was personally impressive and, at first, all business, but eventually became a friend whom I greatly admired.’6

A photographic portrait of Sir Eric Jones taken in 1957 – by which time he had been director of GCHQ for some years – now hangs in the National Portrait Gallery. It shows a handsome, amused figure, slightly loud of suit but neat of hair. Sir Eric was valued on both sides of the Atlantic for his directness. Given his success in the field of commerce, it would not have been unreasonable to have expected him, after the war, to return to the profitable business that he had founded. But in 1946, he told an American colleague that he was keen ‘to stay in the racket’.7

Initially, that top-secret UK–USA agreement excluded Britain’s dominions such as Canada, New Zealand, Australia. They were not even to be privy to the fact that there was such an agreement. And they were not considered for intelligence-sharing because there was concern over how tight security could be over such wide dissemination. But by 1946, following a two-week conference, all that was to change. It was seen as perverse to lock out such formidable intelligence harvesters.

These wrangles aside, this secret alliance opened up vast prospects. Meetings took place in London in 1946, in a smart square just to the north of Marble Arch. Among those sitting in was Sir Stewart Menzies, the head of MI6; and for the Americans, Joseph Wenger. According to Richard Aldrich, when the fine print of negotiations ran into obstacles, it was Menzies who prescribed the age-old British technique for solving such difficulties: he took the American delegation to his St James’s club, White’s, and treated them to a wine-filled lunch. Talks got going again in a more relaxed frame. And then, afterwards, came the signing of the actual agreement: this was carried out, on the British side, by Lieutenant Colonel Patrick Marr-Johnson and on the American by General Hoyt Vandenburg.

Only recently did GCHQ finally acknowledge officially that any such alliance was formed; it was a state secret for over 60 years. There were some good reasons for this: apart from anything else, the blending and sharing of such expertise rendered it an astoundingly powerful force, whereas it was very much in the interests of both Britain and America throughout the entire course of the Cold War that the Soviets should underestimate their abilities and reach.

After the 1946 agreement, the Americans and the British and the dominions between them were listening in on every last square mile of earth. And in strategic terms, the Americans at this stage were leaning heavily on the British; thanks to the UK–USA alliance, they would have regular, secure access to the streams of intelligence being produced by listening stations from Colombo to Hong Kong to Cyprus to Sarafand. In the Indian operation, various listening out-stations were pulling in signals many miles to the north, monitoring all Soviet activity near the borders of Asia with microscopic closeness. Equally, any Soviet transmissions in the Black Sea or the Caspian Sea was being picked up by the British in the Mediterranean.

In archival terms, vast amounts are still being withheld in the UK; in America, slightly more has become available. There are, for instance, very warm letters from US senior codebreaker William F Friedman to Group Captain Eric Jones which the authorities have now placed in the public domain. The correspondence shows an ease and a lightness and a strong sense of mutual respect; there is none of the usually salty efforts on both sides to establish a tone of superiority. Particularly fruitful during this period were the regular bundles of intelligence briefings to do with Russian military movements and build-ups that were passed across the Atlantic. For while there had been some problems with decyphering Soviet military and intelligence codes – and there were far worse problems to come – there was also, by way of consolation, the great innovation of Bletchley Park’s Gordon Welchman: the forensic examination of traffic analysis. That analytical beam was now turned on all corners of the Soviet empire.

For on a day-to-day basis, soldiers had to communicate with soldiers, units with units. And in listening bases across the world, the young British men working the intercepting radios were fast becoming experts in being able to tell individual Soviet radio operators; each operator had their own unique ‘fist’, as distinctive as a walk or a voice. And it wasn’t only the individual techniques for sending Morse messages, it was also the way that these Russian radio operators would communicate with each other outside the official messages being sent. Traffic analysis also yielded up huge amounts of geographical information; by means of direction finding, one could monitor from where messages were being sent, whether certain units were on the move, and where to.

The intelligence alliance was a source of great satisfaction to the Americans. General Charles Cabell, in charge of US Air Force Intelligence (and therefore at the heart of all planning to do with nuclear strike capability) wrote in 1948: ‘At the present time, there is complete interchange of communications intelligence information between the cognizant United States and British agencies. It is not believed that the present arrangements… could be improved.’8

This was not just a new world of interception; it was also very much about the developing technology of signals intelligence gathering, and electronic methods of cracking cyphers. Gordon Welchman, at that time in London working for the John Lewis Partnership, was gnawingly aware of developments in computer technology. Compared to Britain’s efforts – at the National Physical Laboratory in Teddington, and Professor Newman’s department at Manchester University – the Americans were clearly striding ahead. Welchman had kept in touch with some American friends he had made in Bletchley days. It was clear to him that his future lay out there. And even though he had left cryptography behind, it was quite clear that someone with his experience would still be a terrific asset to the United States when it came to technology and questions of national security.

And at Eastcote (or the London Signals Intelligence Centre as it was still being called), Welchman’s old boss Commander Travis was more than happy for him to be farmed out to the US in this way. Since Welchman had been one of the architects of Travis’s new realm in Eastcote, it would have been surprising if this was not so: there was pride (and perhaps an element of healthy competitiveness with the Americans) in sending them such a fine example of British brainpower. However, for an Englishman to be admitted into the most secret spheres of the US state was quite a prospect and, as revealed by Welchman’s biographer Joel Greenberg, Commander Travis provided his old colleague with an unofficial letter of reference. For while Welchman was known within codebreaking circles, he was about to enter quite a different part of America’s labyrinthine defence community.

‘Dear Welchman,’ Travis’s letter read, ‘I have recently been reviewing the wartime work of this organisation with particular reference to the contribution of individual members of the organisation and I should like to place on record my appreciation of the important and outstanding part you played. Your quick mastering of a number of different aspects of the work of which you had no previous experience was most noticeable and your inventiveness and ability in the field of applied mathematics and electronics provided a notable contribution to the success of the organisation.

‘From 1943 to the end of the war,’ Commander Travis continued, ‘your services as an Assistant Director gave you an opportunity to display your organising and administrative ability of which you took full advantage. I hope your wartime experience will be of real value to you in Civil (sic) life in which I wish you every success.’9 While Welchman’s reputation preceded him, Travis’s warm words were themselves a code to do with reliability and discretion, ideal for procuring transatlantic security clearance. The Welchman family set sail in 1948, and Welchman, with that full and very privileged clearance, went to work for an organisation called MITRE.

The British and US trade in codebreakers brought romance to Eastcote. The brilliant cryptographer Joan Malone, while coping with colds, hay-fever and the delicate mores of English suburbia, got to know her colleague and fellow American Captain Harold Callaghan rather better. Love blossomed among those grey one-storey huts; marriage followed swiftly thereafter.

Incidentally, the Americans seemed as forward-looking in their attitude towards the female aptitude for cryptology as Bletchley’s late Dilly Knox, who had always favoured working with women. Back across the Atlantic, at the Arlington Hall cryptography section, more US women were starting to dazzle at this time, including Gene Grabeel. Originally a schoolteacher who grew bored with that work and yearned for something a little more challenging, Grabeel loved her codebreaking life so intensely that she worked with the National Security Agency for a further three decades until the mid-1970s.

Then there was Wilma Zimmerman Davis, a true pioneer in the field. She graduated in mathematics, and, in common with a number of other female US cryptologists, started out as a teacher. But then Davis took US Navy correspondence courses that focused on cryptography. She found that she had a flair; and others had spotted this aptitude too. In the late 1930s, aged 26, she was recruited into the secret realm in Washington DC by the codebreaking pioneer William Friedman. Just months into her new role, Davis was widowed; and she later said that her colleagues at this time became part of an extended family, such was their support. ‘I was a very lucky person that I happened to be there when I lost my husband,’ Davis said. ‘These people gathered around like family and it made life really worth living and going on.’10

She gained terrific experience working first on Italian codes and then on the Japanese Purple system, and even for a little time with Chinese codes. Her expertise was such that she was drafted on to the super-exclusive Venona team. Like so many others, Wilma Davis made a couple of efforts during her later career to leave cryptography behind; but she was always lured back to the work. Indeed, she didn’t actually retire until 1973.

There was also Genevieve Grotjan, the woman now credited by the National Security Agency as having made the first breaks into the Japanese Purple codes. She, too, was drafted on to Venona, and once again provided the agency with an extraordinary means of levering into the codes (though exactly what is still unspecified for security reasons to this day). ‘Miss Grotjan’s brilliant findings in two instances enabled exploitation of communications that provided invaluable intelligence information to policymakers,’ states the agency’s ‘Cryptologic Hall of Honor’ baldly. ‘This information was used by the most senior government officials for decisions in World War Two and the Cold War.’11 Grotjan later married Hyman Feinstein and went off into academia to be a Professor of Mathematics at George Mason university.

‘No two independent powers have ever exchanged as many secrets as Britain and America during and since the Second World War,’ observed historian Christopher Andrew.12 What made these exchanges even more extraordinary was the fact that they were so hermetically sealed: outside the respective codebreaking departments, not even a handful of people knew. The average MI5 and MI6 operatives were not privy to the secret.

Deep in the background, the Venona operation carried on. As well as the British traitors, that enormous tranche of Soviet codes had also ripped away the disguises of American double agents Alger Hiss and Harold Dexter White. Hiss had been a US State Department official. Curiously, his public denouncement as a spy actually came not from the codebreakers but from editor and former Communist Party member Whittaker Chambers who beat them to it at a Senate hearing; when Chambers repeated the accusation of espionage against Hiss on national radio, Hiss sued. But the tactic eventually doubled back on him and he was found guilty of perjury. The point was that even though there were levels of ambiguity and doubt to the Hiss case, it nonetheless seems certain that he was identified in the Venona decrypts. The case of Harold Dexter White was more unsettling: a very senior US Treasury official, Dexter White was among those involved in pulling together the Bretton Woods agreement that put the world’s economies back onto a more stable footing after the war. Again, he was publicly denounced as a spy; more quietly, he was there in that tranche of decrypts. Harold Dexter White never stood trial – but equally, his premature death in 1948, aged 55, meant that he could never deny the successive accusations. There are a few today who maintain that Dexter White’s contacts with Soviet Russia were more innocent than the decrypts appear to suggest.

The Venona messages contained other vital information as well as cover-names; in particular, they opened a significant window into the tactics and methods of the Soviet NKVD, fore-runners of the KGB, by which agents would receive specific instructions to do with conveying their own intelligence (such as how to get rolls of film to their controllers) or indeed simply meeting up – the types of places and times favoured by controllers to meet their agents. They revealed terminology used by the NKVD that these days sounds like pure B-movie spy material: if an agent was to be ‘de-activated’ for instance, the cover term was ‘put on ice’ or ‘put in cold storage’.

But given the tension of the times, this went far beyond simple spy-versus-spy stuff; it is no exaggeration to say that the passing to Moscow of America’s nuclear secrets was one of those acts upon which the world of future generations pivoted. Those Manhattan Project secrets – smuggled out of Los Alamos by the scientist Klaus Fuchs, with help from Julius and Ethel Rosenberg – were to give Stalin the key to true power that he needed.

The story of Klaus Fuchs seems, with the distance of time, many times more extraordinary than the treachery of the Cambridge Spies. Whereas Burgess, Philby, Maclean, Blunt and Cairncross were dealing very often in material involving other spies, Fuchs was handling secret knowledge that would change the tides of power throughout the entire world. Described by one former colleague as a thin-lipped man who never laughed, one might now argue that Fuchs had had little to laugh about. Born in Rüsselheim, Germany, in 1911, he was inspired when young to join the Communist Party. As the thugs of Hitler’s Nazi party became increasingly prominent and confident, Fuchs was targeted, on one occasion being thrown into a river. By 1933, with Hitler now triumphant in the Reichstag, and the Nazis radically transforming Germany’s society and its constitution, he knew that it was time to flee.

First, Fuchs went to Paris; then he came across to England. A gifted physicist, he went to study at Bristol under Nevill Mott; it was there that he gained a doctorate. Later, he moved to Edinburgh University to study under Max Born. These were extraordinary years in the realms of physics; the possibilities suggested by quantum theory were being explored. As art had modernism and futurism, so physics also came to point to a radically different kind of world.

Then, with the outbreak of war, came the official British crackdown on foreign-born nationals – most notably German citizens. Doctor Fuchs was interned along with many fellow countrymen, first on the Isle of Man, and then across the Atlantic in Canada. But the Canadian exile lasted little more than six months in the latter part of 1940; in 1941, Dr Fuchs was permitted to return to Britain.

His story from this point shows the inevitable shortcomings of both signals intelligence and human intelligence. The talented Fuchs was recruited by Rudolf Peierls to work on what sounded a perfectly ordinary war project: ‘Tube Alloys’. It was very far from being ordinary. This was the cover-name for Britain’s effort to develop the atomic bomb. Fuchs, having signed the Official Secrets Act, was also given British nationality; no sounder precautions were felt to be necessary.

It was a serious mistake on the part of the British. Indeed, as soon as he had been drafted into Tube Alloys in 1941, Fuchs had determined that the Soviet Union should share in this awful new power. His decision came at around the point that the Germans had consigned the Molotov-Ribbentrop non-aggression pact with the Soviet Union to the flames and launched their invasion of Russia. It is possible to see the anguished idealism that would lead a young Communist to seek to do anything to help the bloc that he considered to hold the prospects for a brighter, cleaner future.

And so it was that Fuchs had made early contact with the Soviets in London, and established regular meetings where he passed everything on. Around this time, John Cairncross, who was working at Bletchley, was also meeting up on a regular basis on the outskirts of London with Soviet agents. It seems quite surprising that Fuchs was not being monitored; what came next was more startling still.

By 1943, Fuchs and Rudolf Peierls were invited by the Americans to join forces. The scientists set sail for the US, working first in New York and then at Los Alamos deep in New Mexico, on what was being termed the Manhattan Project.

Dr Fuchs was to become more than just a valued colleague: presiding genius Robert Oppenheimer had frequent close and detailed conversations with him. And here we might see some of Fuchs’s native courage, no matter where one stands on his actions. For he contrived to start getting secrets out of the most secure site on earth. Here was a man working not merely with equations on a blackboard, but next to the physical reality of the bomb itself. Obviously, security in and out of the Los Alamos site was extraordinarily tight, but Fuchs had no need to smuggle reams of documents. He had a diamond-sharp mind.

And so it was, after all those detailed discussions and debates with Oppenheimer, that Fuchs would then leave the base, travel to another small, obscure town in New Mexico, and there meet with his Soviet contact. The contact would make notes; Fuchs had the fine detail memorised – unimaginably fine, ranging from the critical mass of fissile material to the complex inner workings of the bomb structure. He simply felt it his duty: this was the technology that was going to decide the future of the world, and there was no way that the Soviet Union could be allowed to fall behind in the arms race.

His treachery would eventually be uncovered; but his unmasking would come only after the entire world had stopped in shock when Stalin detonated the Soviet bomb.

In the meantime, Fuchs returned to England after the war, welcomed closer than ever into an appreciative scientific community. Indeed, he was made head of the Theoretical Physics Division at the brand new Atomic Energy Research Establishment at Harwell. Fuchs also sat on many advisory committees, and he continually advised the need for ever tighter security around Britain’s own burgeoning nuclear projects.

In the end, it was the Venona codebreakers who revealed his activities; old messages would eventually be unscrambled that made references to Los Alamos. Given the limited numbers of people who had that sort of high-level access, his identity was finally pinpointed and GCHQ helped ensure, in circumstances of the greatest secrecy, that this intelligence was passed to MI5. They would also uncover a startling postscript to the Fuchs story.

In espionage terms, the grab for the bomb was not the only Soviet gambit uncovered by the Venona programme. There was huge Soviet appetite for learning via espionage about the nascent field of jet-engine technology, for instance; or in the advances made in the area of rocket science. The Soviets were desperate to know more about the development of jet aircraft, and the new capabilities that such materiel might bring. The atomic secret was one thing; but to acquire as well the means to deliver such doomsday weapons, in a matter of minutes, either from screamingly fast planes, or by missiles that could fly across countries… That would instantly change the landscape of power.

But incredibly, the Venona secret itself was also compromised, in circumstances that were almost blackly comic. For among the very few who were invited in on the intelligence that these Soviet codes had been cracked were in fact two undercover Soviet agents. In the US, that agent was Elizabeth Bentley. For the British, it was the Cambridge Spy Kim Philby.

London and the south-east of England formed an extremely important axis: the Venona decrypts also revealed that there was a female agent working in the area of Oxford, who was key in passing on signals from Klaus Fuchs without her secret radio equipment being detected. In the messages, she was referred to as SONIA (and later acquired the nickname ‘Red Sonia’). This was Ursula Beurton, who had managed to evade the attentions of the Radio Security Service by concealing a large transmitter within a stone garden wall.

This was not abstract paranoia, or a deliberate demonising of the Eastern Bloc. Rather, there was real anxiety. Venona exposed the most frightening vulnerability – first, as to the extent to which the Soviets had captured the hearts and minds of so many key British and American operatives; and second, the way that this capture had enabled the Soviets to acquire the gift of nuclear firepower. In Britain, even some regarded as being far to the left looked with misgivings across the Channel, into the darkness of that smouldering, smashed-up continent. They could hear the approach of the Soviet tanks from the east. Daily, they would read reports about Soviet progress in countries such as Hungary and Romania: the machinations by which elected politicians were gradually being replaced with Soviet sympathisers, making it easier for the Kremlin to absorb fresh territory without even firing a shot. And it was in Germany that all these anxieties would reach an early pitch, in the 1948 crisis that marked the start of open, formal hostilities in the Cold War. The secret listeners feeding messages back to the London Signals Intelligence Centre at Eastcote were intercepting communications that could decide the fate of Europe for an age to come.