The Secrets of Station X

by Michael Smith

  The mix of young female secretaries and rather elderly and eccentric male codebreakers, many of whom had worked in Room 40 or its War Office equivalent during the First World War, scandalised the staff of the hotels where they were staying. The head of the Naval Section ‘Nobby’ Clarke, by now fifty-five years old, recalled booking into the Bridge Hotel in Bedford with two male and three very young female colleagues. ‘The men were all in their late fifties and the females somewhat younger,’ Clarke said. ‘Each day to the astonishment to the hotel staff they all went off in a car and did not return until late in the evening. It seems to have been thought that these must be a party of elderly gentlemen with their young women. A chambermaid at the hotel who was complaining of over-work, on being told that times were serious and that she should not complain, said: “It’s alright for you, but some of us have to work.” Little did she realise what these odd people were doing.’

  The chef sent in by Sinclair was in fact his favourite chef from the Savoy Grill and the meals were very much haute cuisine. But after a few days of trying to deal with the demands of the some of the more difficult codebreakers, the chef also attempted suicide. Clarke was forced to telephone the Buckinghamshire Chief Constable in an attempt to keep the story out of the papers and ensure that the codebreakers’ presence at Bletchley Park remained secret. ‘Then we learned that Chamberlain had flown to Munich and made an agreement with Hitler,’ Cooper recalled. ‘We all trooped back to London with mixed feelings of shame and relief.’

  Despite Chamberlain’s claims of ‘peace in our time’, all he had actually done was buy time, at the expense of the Czechs, for Britain to prepare for war. The race to break the Enigma cyphers now had added urgency, but despite his undoubted brilliance Dilly Knox was having no success. In search of an answer, Denniston invited his opposite number in the French Deuxième Bureau, Colonel Gustave Bertrand, to London. The meeting was so secret that it was held away from Broadway Buildings with Bertrand referred to, even in correspondence between Denniston and Sinclair, as ‘Mr X’.

  The British had exchanged information on Russian cyphers with the Deuxième Bureau’s codebreaking operation since 1933. But it was not until late 1938 that the two sides began to discuss the Enigma machine in any detail. Given that the exchange on Russian material had been somewhat one-sided, with the British providing far more than they received in return, the French had a surprisingly large amount of material on the Enigma machine. Denniston wrote to Sinclair suggesting that the dialogue was worth continuing. The French had clearly not got far themselves but had produced some 100 documents, some of which were of more value than others. They included ‘photographs of documents relating to the use of the Enigma machine which did increase our knowledge of the machine and have greatly aided our researches’, Denniston said. Bertrand made clear that some of the French material had been obtained by secret agents. In fact, it was largely from one Deuxième Bureau agent codenamed Asche.

  Hans Thilo Schmidt worked in the German War Ministry’s cypher centre and, in exchange for money and sex, had provided the French with comprehensive details of the Wehrmacht Enigma systems. Schmidt was a ‘walk-in’, calling at the French embassy in Berlin in 1931 and offering to sell them documents on the use of Enigma in return for 10,000 marks. The critical handover came at a meeting between Asche and Bertrand at a hotel at Vervier, on the French-German border, in late 1932, when Asche produced two operators’ manuals, one of which had a message which had been encyphered using a real Enigma machine, and a schedule of daily Army keys for September and October 1932. They were photographed by the French allowing Asche to return the documents to the safe in the German War Ministry from which he had taken them before their absence could be spotted. Over the next six years, Asche produced numerous documents which were offered to the British and – until the November 1938 meeting with ‘Mr X’ – turned down, but which were passed on to the Poles.

  Following the meeting with ‘Mr X’, Denniston asked Sinclair’s permission to continue the liaison with the French, explaining that

  our main reason for seeking this liaison in the first place was the desire to leave no stone unturned which might lead to a solution of the Enigma Machine as used by various German services. This is of vital importance for us and the French have furnished us with documents which have assisted us but we are still doubtful if success can be obtained without further documents. During the coming meetings, we hope to show Mr X the lines on which we are working and make clear to him what other evidence we need in the hope that his agents may produce it.

  The liaison with the French brought GC&CS a number of interesting documents, Cooper recalled. Since they arrived via the MI6 station in Paris in the same red jackets the British secret service used for all its reports, the French contributions were nicknamed ‘Scarlet Pimpernels’. They included documents on how to use the machine as well as photographs showing the Stecker system and how it worked, Cooper recalled. They also suggested that the French were not working alone.

  They had not disclosed that they had other signals intelligence partners. But a Scarlet Pimpernel on the German Air Force Safety Service traffic had obviously been produced from material intercepted not in France but on the far side of the Reich. It gave data on stations in eastern Germany that were inaudible from Cheadle, but was weak on stations in the north-west that we knew well. Eventually, the French disclosed that they had a liaison with the Poles, and three-sided Anglo-Franco-Polish discussions began on the Enigma problem.

  Denniston, Knox and Foss attended a meeting in Paris in early January 1939 with the French and representatives of the Bureau Szyfrow, Polish codebreaking organisation. The British codebreakers had high hopes that the meeting with the Polish codebreakers would help them to find a way to break Enigma. But it was to be a major disappointment. All three sides appear to have been too cautious to give anything of value away with Denniston describing the conference as having been held in ‘an atmosphere of secrecy and mystery’. The French codebreakers explained their own method of breaking Enigma, which was even less refined than the basic system used by Foss in 1927. Knox described his improved version of Foss’s system, which used a process known as ‘rodding’. The Poles were under orders to disclose nothing substantive and explained only how lazy operators set the machines in ways that produced pronounceable settings, such as swear words or the names of their girlfriends. This was something the British had already worked out and it was a great disappointment that they had nothing more to add, Foss recalled. ‘Knox kept muttering to Denniston, “But this is what Tiltman did,” while Denniston hushed him and told him to listen politely. Knox went and looked out of the window.’

  Knox was dismissive of the claims made by both the French and the Poles, in the latter case wrongly but largely because the officer explaining them was clearly not a codebreaker himself and did not speak with any authority on the subject. Knox’s assessment of the Polish work was damning: ‘Practical knowledge of QWERTZU Enigma nil. Had succeeded in identifying indicators on precisely the methods always used here, but not till recently with success. He [the Polish officer] was enormously pleased with his success and declaimed a pamphlet, which contained nothing new to us.’

  The main problem for Knox was what he called ‘the QWERTZU’, by which he meant the way in which the letters on the keyboard of the Wehrmacht Enigma machines were wired to the letters on the wheels inside the machine, and he left the meeting in Paris none the wiser. One good thing did however come out of the January 1939 meeting. It became clear that the Poles were using mathematicians to try to break Enigma and, when they returned to the UK, Denniston recruited two mathematicians to assist Knox. One was Alan Turing, a 27-year-old fellow of King’s College, Cambridge, who began working part-time, coming in on occasional days with the intention of joining full time when the war began. The other was Peter Twinn, a 23-year-old mathematician from Brasenose College, Oxford, who started work immediately.

  ‘When I joined GC&CS in early Febru
ary 1939 and went to join Dilly Knox to work on the German services’ Enigma traffic, the outlook was not encouraging,’ Twinn recalled. Knox and the other leading GC&CS codebreakers were largely classicists or linguists, he said.

  They regarded mathematicians as very strange beasts indeed and required a little persuasion before they believed they could do anything practical or helpful at all. The people working on Enigma were the celebrated Dilly Knox and a chap called Tony Kendrick, quite a character, who was once head boy [Captain of the School] at Eton. There was a slightly bizarre interview from Dilly who was a bit of a character to put it mildly. He didn’t believe in wasting too much time in training his assistant; he gave me a five-minute talk and left me to get on with it, which was actually rather good for me. Before I arrived Dilly was a lone hand, he always was, assisted by one secretary/ assistant and enjoying a total lack of other facilities – though it is by no means clear that he would have used any. He was notorious for being very secretive about his ideas and I am not sure whether he had any hopes of ultimate success.

  Dilly Knox was an exceptional man whose brilliance has only rarely been acknowledged. With the possible exception of John Tiltman, Knox was the only codebreaker of this era who proved as adept at breaking the old-fashioned codebooks of the First World War as the machine cyphers of Second World War. The son of a bishop, and the brother of the Roman Catholic theologian Ronnie Knox, he was fifty-five at the start of the war and so wildly eccentric as to put his fellow codebreakers in the shade. A fellow of King’s College, Cambridge, he walked with a limp, the result of a motorcycle accident, and wore horn-rimmed glasses without which he could see nothing. Knox was so absent-minded that he forgot to invite two of his three brothers to his own wedding. He believed so strongly in the relaxing powers of a bath to give him inspiration that during the First World War he had a bath installed in a room in the Admiralty. A fellow codebreaker recalled how, early in the war, the fellow lodgers in Knox’s billet became so concerned at the length of time he was spending in the bathroom that they felt compelled to break in. ‘They found him standing by the bath, a faint smile on his face, his gaze fixed on abstractions, both taps full on and the plug out. What was passing in his mind could possibly have solved a problem that was to win the war.’

  Knox was in fact very close to breaking Enigma and there was just one major thing that was holding him up, Twinn recalled.

  What we did not know was the order in which the letters of the keyboard were connected to the twenty-six input discs of the entry plate. Dilly, who had a taste for inventing fanciful jargon, called this the QWERTZU. We had no idea what the order was. We had tried QWERTZU, that didn’t work. There are twenty-six letters in the alphabet. Our ordinary alphabet has them in a certain order, but the Germans weren’t idiots. When they had the perfect opportunity to introduce a safe-guard to their machine by jumbling it up that would be the sensible thing to do. After all, there were millions of different ways of doing it.

  The introduction of mathematicians to help Knox in his investigations of the Enigma problem was fortunately not the only good thing to come out of that first meeting with the Poles in Paris in January 1939. Knox might not have been initially impressed with the Poles, but they were certainly impressed with him and specifically asked that he be present at a second meeting between the Polish, British and French codebreakers, to be held at the Bureau Szyfrow, the Polish cypher bureau, in the Pyry Forest just outside Warsaw, in July 1939. It was only then that the Poles revealed the full extent of the progress they had made in reconstructing the Wehrmacht’s steckered Enigma machine.

  The Bureau Szyfrow had broken a number of German codes during the early 1920s but the introduction of Enigma had left them unable to read the Wehrmacht’s messages. Their response was to recruit mathematics students and put them through a codebreaking course. Only three passed. Their names were Jerzy Różycki, Henryk Zygalski and Marian Rejewski. All three were recruited but worked initially on a part-time basis and it was only in September 1932 that Rejewski, the best of the three, was given the steckered Enigma machine and asked to solve it. By the end of that year, assisted by Enigma key lists obtained by the French from Asche, he had reconstructed the wiring mathematically, using permutation theory. By the beginning of 1938, assisted by the fact that the Germans were not changing the settings frequently, Rejewski and his colleagues were able to solve 75 per cent of the Poles’ intercepts of German Army Enigma messages. ‘We were decyphering every day and often at a record speed,’ he recalled.

  In the autumn of that year, they began using electro-mechanical machinery known as Bomby – literally ‘bombs’, a name that derived from the ticking noise they made. The Bomby were used to identify ‘females’, repetitive letters in the Enigma keys, to break the messages. But the introduction, in December, of two additional wheels, allowing further different permutations of wheel order, brought the Polish successes to a halt. Rejewski succeeded in reconstructing the wiring of the two new wheels but the Poles no longer had enough Bomby to run through the much greater number of possibilities the new wheels had created. They needed help and believed the British could provide it, said Colonel Stefan Mayer, the officer in charge of the Bureau Szyfrow. ‘As the danger of war became tangibly near we decided to share our achievements regarding Enigma, even not yet complete, with the French and British sides, in the hope that working in three groups would facilitate and accelerate the final conquest of Enigma.’

  The Poles explained how they used the Bomby and the Netzverfahren or ‘grid system’ invented by Zygalski. These were lettered sheets of paper with holes punched in them to help to break the keys and wheel orders by identifying the ‘females’. But the introduction of the fourth and fifth wheels had meant they had to use far more Bomby and sheets than they could possibly produce. Knox was furious to discover that the Poles had got there first, sitting in ‘stony silence’ as they described their progress and produced a clone of the Enigma machine, reconstructed using the knowledge they had built up over the previous six years. But his good humour soon returned after they told him that the keys were wired up to the encypherment mechanism in alphabetical order, A to A, B to B, etc. Although one female codebreaker had suggested this as a possibility, it had never been seriously considered, Twinn recalled. ‘It was such an obvious thing to do, really a silly thing to do, that nobody, not Dilly Knox or Tony Kendrick or Alan Turing, ever thought it worthwhile trying,’ he recalled. ‘I know in retrospect it looks daft. I can only say that’s how it struck all of us and none of the others were idiots.’

  A few weeks later the Poles gave both the French and British codebreakers clones of the steckered Enigma. Bertrand, who had been given both machines and asked to pass one on to the British, later described taking the British copy to London on the Golden Arrow express train on 16 August 1939. He stepped down from the train at Victoria station to find the deputy head of MI6 Colonel Stewart Menzies standing on the platform, swathed in smoke and wearing a dinner jacket on which was pinned the rosette of the Legion d’Honneur. Bertrand handed the machine over to Menzies with the words, ‘Accueil Triomphal’ – ‘a triumphant welcome’.

  As well as setting up the meetings with the French and the Poles, which would ultimately give the British the additional information they needed to break Enigma, Denniston began building up the organisation for war, touring the universities to search out academics, particularly mathematicians, linguists and classicists, with potential to become the new codebreakers his organisation would desperately need to first break the German cyphers and then keep on top of them. Sinclair got authorisation from the Treasury for the recruitment of ‘fifty-six senior men or women, with the right background and knowledge’ as well as thirty young female language graduates. Josh Cooper recalled:

  It was often said, in the old GC&CS, that if we had another war we should have to mobilise the dons again. Denniston now went on a round of visits to the universities in order to sound out his former colleagues from the 1914–18 wa
r, to find whether they would be prepared to rejoin in an emergency, and whether they could introduce him to other university teachers who might be useful and would be prepared to come. He dined at several High Tables in Oxford and Cambridge and came home with promises from a number of dons.

  Denniston, who was by now fifty-seven, recalled that

  it was naturally at that time impossible to give details of the work, nor was it always advisable to insist too much in these circles on the imminence of war. At certain universities, however, there were men now in senior positions who had worked in our ranks during 1914–18. These men knew the type required. Thus it fell out that our most successful recruiting occurred from these universities. During 1937 and 1938 we were able to arrange a series of courses to which we invited our recruits to give them a dim idea of what would be required of them.

  The ‘territorial training course’ lasted about a fortnight; the first day was taken up with security indoctrination, after which the trainees visited a number of sections spending two or three days in each, with programmes arranged to suit the interests and qualifications of individuals. At the end of the course they were asked to say whether they would undertake to come to Bletchley on receipt of a telegram, and to say which section they would prefer to work with. Their pay was fixed at £600 a year with their colleges making up the balance of their normal salaries. The young female language graduates were not so fortunate, receiving just £3 a week.

  Denniston is in many ways a tragic figure, never given the credit he deserved for his astute decision to work with the French, which led to the cooperation with the Poles, and to bring in mathematicians, a proposition that was never going to be welcomed by many of his more experienced staff. He would later be unceremoniously pushed aside and when he died in 1961 there were no obituaries pointing out the good work he had done for his country. But the work he put into recruiting academics, and particularly mathematicians, and preparing them to be called up on the outbreak of war showed a large degree of prescience and, as Cooper recalled, laid the foundations for the breaking of the Enigma cyphers that was to make such a major contribution to the Allied war effort.