SOE was a widely known secret within Whitehall. By contrast, Bletchley Park was not – with a few exceptions, even the inhabitants of Churchill’s private office knew nothing of Ultra: his various private secretaries who handled the mysterious boxes of intercepts only became aware that they had contained Ultra material in the 1970s. The boxes arrived in Number 10 with a strict notice: ‘Only to be opened by the prime minister.’ The secretaries placed them on the prime minister’s desk, ‘and left [them] for him to re-lock’. The Ultra secret really was ultra-secret – even in Downing Street.44
Bletchley Park was only one part of the vast sigint operation presided over by GC&CS. The British codebreaking empire, which numbered some 10,000 people by the end of the war, also intercepted diplomatic traffic (‘flimsies’, also known as ‘BJ’s, or ‘blue jackets’, after the colour of their folders) from dozens of countries. This material was full of political gossip, and Churchill characteristically found it irresistible. His favourite reading included seemingly obscure stuff, such as messages from the Brazilian ambassador in London. The volume was incredible – reaching 13,000 messages in 1941 and increasing dramatically thereafter. It was Morton’s job to sift through this material, selecting those messages that he knew would interest the prime minister.45
Stewart Menzies also brought Churchill human agent reports, known as ‘CX’, from MI6. On the whole, though, MI6 and its human intelligence – or ‘humint’ – underperformed, and Menzies found the flow of decrypts from the codebreakers vital in terms of both maintaining his personal standing and defending the reputation of MI6 within Downing Street. In Europe he was also able to piggyback to some degree on the governments-in-exile by trying to restore their agent networks in Europe, but in other regions, including the Far East, MI6’s wartime performance was weak. In August 1940, a teleprinter circuit connected the MI6 headquarters at Broadway Buildings in St James’s with Downing Street, where Group Captain F.W. Winterbotham helped Menzies to select the ‘headlines’ for Churchill.46 One MI6 agent, codenamed ‘Knopf’, did provide Menzies and Churchill with valuable intelligence on Hitler’s plans for the Eastern Front and the Mediterranean – including the location of the so-called ‘Wolf’s Lair’, Hitler’s headquarters in eastern Prussia. Knopf and his sub-network provided access to the upper echelons of the Third Reich, informing London that, for example, the Führer was ‘determined to capture Stalingrad at all costs’.47 For the most part, however, Menzies relied on sigint.
Unlike Menzies, Churchill adored science, and depended heavily on his scientific adviser ‘Prof’ Frederick Lindemann. Meeting Churchill almost daily, Lindemann enjoyed more influence than any other civilian adviser. Together they helped to create an entirely new form of scientific spying that would come to be called ‘electronic intelligence’. On 12 June 1940, one of Lindemann’s protégés, a young Oxford scientist working for MI6 called R.V. Jones, was asked by the head of the RAF element that worked with Bletchley Park about a puzzling reference to something called a ‘Knickerbein’, or ‘crooked leg’. No one could understand what it was for. Jones developed a theory that the Germans were using radio beams to guide their bombers. The bizarre theory, unsurprisingly, made its way back to Churchill. Shortly afterwards, a captured German flier gave some details of the system under interrogation: when two radio beams intersected, the bombs were dropped automatically and found their target.
On 21 June, Churchill summoned Jones to Downing Street. Ushered into the Cabinet Room, he found himself sitting with the prime minister, his former Oxford tutor Lindemann, and an array of advisers. Jones was only twenty-eight, but was unabashed by the company – he knew the business was simply ‘too serious’. He sensed a lack of comprehension around the table, and decided to tell his tale like a detective story. Churchill, predictably, was captivated, and he described the collective fascination in the room as ‘never surpassed by the tales of Sherlock Holmes’. Without informing the cabinet or the chiefs of staff, he ordered that the existence of the German radio beams be assumed, ‘and for all countermeasures to receive absolute priority’, before adding that the ‘slightest reluctance or deviation … was to be reported to me’. Churchill later recalled that ‘in the limited and … almost occult circle obedience was forthcoming with alacrity, and on the fringes all obstructions could be swept away’.48
The prime minister’s response to the inspired deductions of Jones brilliantly captures his effect on intelligence. Impulsive and romantic as he was, his interventions could be critically important, and often inspired immediate action when the machine had become slow. The RAF created an entire special unit called ‘80 Wing’ to jam the German beams with a counter-weapon codenamed ‘Aspirin’. Sometimes this simply bent the beams, causing the Luftwaffe to drop their bombs in the wrong place. In September 1940 the Germans came up with a new system called the ‘X-beam’, and Jones had to create a new jamming system, codenamed ‘Bromide’. Churchill is often associated with the now heavily debunked story that he allowed Coventry to be bombed to save the secret of Ultra. In fact, the reverse is true. He was at the forefront of deploying a new form of intelligence that saved many of Britain’s cities from greater bombardment just before the onset of the Blitz in the autumn of 1940.49
A year later, the prime minister visited Bletchley Park. On 6 September 1941, he was escorted into the famous huts, and Alan Turing was asked to tell him about the remarkable mathematical triumphs that had been accomplished there. Being a rather shy character, Turing allowed his colleague Gordon Welchman to take over. Before he could finish, the director, Alastair Denniston, interrupted and moved Churchill on. Welchman later fondly recalled: ‘whereupon Winston, who was enjoying himself, gave me a grand schoolboy wink’. The prime minister moved on to tour the machine room in Hut 7. His bodyguards tried to follow him in, but the sentries shouted ‘Not you!’ so they waited obediently outside. Here Churchill could see intelligence being produced on an industrial scale, with forty-five machine operators in action.
He stood on a pile of bricks and gave an impromptu address to some of the codebreakers. ‘You all look very innocent; one would not think you knew anything secret.’ He explained that he called them ‘the geese that lay the golden eggs – and never cackle!’ With deep emotion, he explained how grateful he was for all their work, and how important it was. Privately, he was struck by the informality of the place and its eccentric inhabitants: it reminded him more of a university common room than a military camp. Winding down the window of his car, he said to Denniston, ‘About that recruitment – I know I told you not to leave a stone unturned, but I did not mean you to take me seriously.’
Churchill would have been shocked to know that all was not well at Bletchley Park. Managed by MI6, some of whose officers struggled to understand technology, the codebreaking operations were starved of resources. With Germany’s new Enigma keys coming on stream and a vast amount of fresh material to process, the situation soon reached breaking point, and some of the codebreakers Churchill had met on his visit elected to write to him personally. On 21 October 1941, the anniversary of the Battle of Trafalgar, Stuart Milner-Barry, a chess champion turned Bletchley cryptanalyst, was given the unenviable task of conveying their letter to the front door of 10 Downing Street and handing it to a bemused official. The letter thanked Churchill for his visit, and continued:
We think, however, that you ought to know that this work is being held up, and in some cases is not being done at all, principally because we cannot get sufficient staff to deal with it. Our reason for writing to you direct is that for months we have done everything that we possibly can through the normal channels, and that we despair of any early improvement without your intervention … it is very difficult to bring home to the authorities