The Bletchley Park Codebreakers

by Michael Smith

  Cooper already knew Fetterlein, having been introduced to him by one of the teaching staff at King’s College.

  His experience and reputation were both great, and I was fortunate to find myself assigned to work with him on Soviet diplomatic, which at that time consisted of book ciphers, mostly one part, reciphered with a 1,000-group additive key. He took very little notice of me and left it to an army officer who had been attached to GC&CS, Capt. [A. C.] Stuart Smith, to explain the problem and set me to recover some Russian additive key. Traffic was scanty and it was hard to get adequate depth. Also the book I was working with had been solved in India by Tiltman and Col. Jeffrey and nobody had worked on it at home. It took me some time to realize that almost every group had two meanings. After about six weeks’ work, during which I rubbed holes in the paper with endless corrections, at last I read my first message which was from Moscow to the Soviet representative in Washington and was concerned with repudiation of debts by American states.

  Despite Cooper’s problems with the cipher he was put to work on, the amount of Soviet messages continued to increase with the opening of a new Royal Navy intercept site at Flowerdown, near Winchester, an army site at Chatham, and an RAF site at Waddington, in Lincolnshire. Sinclair moved both the code-breakers and his MI6 staff to a new joint headquarters at 54 Broadway, close to Whitehall, in 1925. He also added to the intercept facilities by co-opting the resources of a small Metropolitan Police intercept operation, which was run by Harold Kenworthy, an employee of Marconi who was on indefinite loan to the police. It operated out of the attic at Scotland Yard, employing a number of ex-naval telegraphists to intercept illicit radio stations.

  The Metropolitan Police unit had first shown its capabilities during the 1926 General Strike. Although the strike broke out largely for socioeconomic reasons, the BJs had shown the Soviet Government keen to provoke industrial action to the extent of subsidizing the striking miners to the tune of £2 million. It was scarcely surprising therefore that when, on the first day of the General Strike, the Metropolitan Police operators intercepted an unusual wireless transmission using apparently false callsigns and emanating from somewhere in London, there were suspicions of Russian foul play. Kenworthy informed the assistant commissioner in charge of the Special Branch who in turn contacted Admiral Sinclair. The MI6 Chief sent over the GC&CS radio expert Leslie Lambert, better known as the BBC ‘wireless personality’ A. J. Alan, and together they constructed a miniature direction-finding device small enough to fit into a Gladstone bag, Kenworthy recalled.

  The portable set was put to good use. Influence by Assistant Commissioner and SIS [MI6] made it possible to get access to roofs of buildings in the vicinity of the suspected source of signal which had been roughly located by taking a completely empty van and sitting on the floor with the Gladstone bag. It was gratifying that the work put in was finally rewarded by actually ‘walking in’ from the roof tops into the top of a building housing the transmitter whilst the operator was using it. The result was an anti-climax as the transmitter had been set up by the Daily Mail, who thinking that Post and Telegraph personnel would be joining the strike at any moment, decided to try and be ready for a ‘coup’. The call sign AHA was derived from [the newspaper’s proprietor] Alfred Harmsworth. As a matter of high policy nothing was ever published about this exploit.

  The illicit radio transmitter may not have been run by the Russians, but the General Strike and Moscow’s attempts to inspire revolution in China and to take control of Afghanistan – and thereby threaten India – increased the general feeling within the Conservative-led establishment that the Bolsheviks were determined to subvert Britain and its Empire.

  Government ministers were also influenced by MI5 and Special Branch reports of Soviet espionage centred on ‘the firm’, a cover name for the All-Russian Co-operative Society (ARCOS) based in Moorgate, ostensibly set up to facilitate trade between Britain and Russia. None were anywhere near as successful as the later Cambridge spy ring, but their attempts to obtain military and naval intelligence outraged those like the intensely anti-Bolshevik Home Secretary Sir William Joynson-Hicks, who put pressure on the then Foreign Secretary Sir Austen Chamberlain to back action against Russia. Throughout 1926, Chamberlain continued to defend his policy of pragmatic dealing with Moscow rather than lose the new trade links. But by 19 January 1927, he accepted that there was a need ‘to review in Cabinet our relations with Russia’, asking the President of the Board of Trade what Britain’s ‘actual trade interests’ amounted to, and for some sense of ‘the sentiment of traders’ about them. Five days later, he drafted a protest note to the Russians. He suspected that it would not satisfy Joynson-Hicks, or the other hardliners like Winston Churchill, now Chancellor of the Exchequer, and he was right. But it was the start of a process that would soon lead to a complete diplomatic break with Moscow.

  What exactly made Chamberlain accept the need for action is still unclear. But some time during 1926, the codebreakers had received a new source of telegrams. MI6 had already managed to acquire the Bolshevik cables passing through the Tehran post office, of crucial interest with regard to Russian threats to Afghanistan. Now it supplied the Soviet telegrams sent via Peking, allowing the codebreakers to break complete substitution tables for the first time and producing a rich harvest of intelligence for the cabinet hardliners. The addition of Alfred Dillwyn ‘Dilly’ Knox to Fetterlein’s team may well have contributed to this success. Dilly’s early promise at Eton – he beat John Maynard Keynes to take first place in the scholarship for King’s College, Cambridge – had been confirmed by his work in Room 40, where he and Nigel de Grey broke the Zimmermann Telegram in January 1917. Six days before Chamberlain’s letter to the President of the Board of Trade, Knox’s work had given him an unexplained reason to celebrate. He bought himself a new Burberry overcoat and ordered dinner at an expensive restaurant. ‘These expenses might pass as unremarkable,’ his niece Penelope Fitzgerald recorded in The Knox Brothers. ‘But with Dilly they could only mean celebration and it is at least possible that the Government had agreed, in his own phrase, to “get something from the post office”.’

  Whatever the celebration was about, the messages obtained from the Peking post office were to have a devastating effect on Anglo-Soviet relations. Over the ensuing weeks, further examples of Soviet espionage were detected and on 12 May, the police raided the ARCOS headquarters. The Russians had been warned of the impending raid and, despite three days of searching by the police, nothing of significance was discovered.

  In order to justify the decision to break with Moscow, the Prime Minister Stanley Baldwin resorted to reading out the text of some of the deciphered Peking telegrams in Parliament. He was followed two days later by Chamberlain who, reminding MPs that there had been a recent anti-British demonstration outside the British embassy in Washington, read an extract from a message sent a month earlier by Moscow to its representatives abroad. Clearly taken from a deciphered intercept, it said: ‘It is absolutely essential to organize in the shortest possible space of time meetings against England and to demonstrate where possible in front of British embassies and legations.’ Chamberlain followed this extract from one of the decrypts with a succession of other examples. Although these were at least paraphrased rather than quoted verbatim, the Russians had got the message. Where they had previously been slow to change their cipher systems, they now adopted the one-time pad system (OTP), which if used properly was impossible to break.

  The codebreakers were horrified. There was a brief period during which the old ciphers continued to be used in more remote places like Central Asia. But very soon the decipherable diplomatic messages dried up. ‘HMG found it necessary to compromise our work beyond any question,’ recalled Denniston. ‘From that time, the Soviet Government introduced OTP for their diplomatic and commercial traffic to all capitals where they had diplomatic representatives.’

  Josh Cooper, speaking with the benefit of hindsight, after misuse of the system had led
to at least two other one-time pad systems being broken, said that it might have been possible to break the Soviet diplomatic system if only there had been enough codebreakers to allow ‘long shots’.

  Tiltman went so far as to read a few groups of “wrapover” texts when a pad was used to a depth of two at the end of some messages. This we felt to be interesting but of little practical value. It might, however, if persisted in, have led to the discovery of re-use of pads. We knew from previous experience of their old diplomatic systems that the Russians were capable of re-using additive tables.

  Although the Russian diplomatic material had dried up, the Soviet Union provided GC&CS with a second interwar success via the communications of the Comintern, the organization set up in 1919 to promote communism and revolution around the world. It controlled all of the various communist parties, each of which formed a so-called ‘Section’ of the Comintern and was bound to follow its direction. They were also required to set up parallel ‘illegal’, or more accurately underground, organizations that would be controlled by the Comintern in order to prepare for a general strike and armed insurrection that it was hoped would precede fresh revolutions. An additional role of these ‘illegal’ organizations was to carry out espionage.

  The first sign of illicit transmissions linking the Communist Party of Great Britain to Moscow came in early 1930, when the various intercept units began picking up a large number of unauthorized radio transmissions between London and Moscow. ‘Peacetime GC&CS did have one experience of successful work on clandestine traffic,’ Denniston recalled. ‘This, unlike the diplomatic, necessitated close co-operation between interception, T/A [Traffic Analysis] and cryptography before the final results were made available only to a small select intelligence section of SIS.’ The operation, codenamed Mask, was run by Tiltman, who had returned from India in 1929 with a great deal of experience in Soviet wireless and cipher practice. ‘The analysis of this traffic was studied closely and from it emerged a world-wide network of clandestine stations controlled by a station near Moscow,’ Denniston recalled. ‘It turned out to be the Comintern network.’ The attack on the Comintern ciphers ‘met with complete success’, he said.

  The ‘small, select’ MI6 section to which the decrypted material was sent was the two-man counter-espionage department known as Section V (five). It was led by Major Valentine Vivian, a former Indian police officer. The material was also discussed with B Branch of MI5, which at the time was responsible for Soviet subversion and espionage. J. C. ‘Jack’ Curry, who was in charge of MI5 operations against subversion for part of the 1930s, recalled that the messages dealt with a variety of subjects. ‘The London/Moscow transmissions were part of a large network with a number of stations in different parts of the world and the material dealt with a variety of the affairs of the Comintern and its sections in different countries. Those from Moscow included directions and instructions regarding the line to be taken in propaganda and in party policy generally. They gave, among other things, details regarding subsidies to be paid by Moscow, a large part being allocated to the Daily Worker.’

  Many of the messages were obscure and difficult to understand without an appreciation of the context and the cover names of those to whom they referred. Curry said. ‘Major Vivian was, however, able to extract useful intelligence from a number of messages and, in particular, obtained a certain picture of some of the details of Comintern finance and its measures for subsidising its Sections in other countries. Information about the names of couriers and active Communists, including certain British crypto-communists, was obtained from this source.’

  The information culled from the Comintern decrypts appears to have allowed MI6 to recruit a number of agents inside the Comintern in France, Holland and Scandinavia. But the best source it had within the Comintern was a ‘walk-in’, a spy who offered his services to MI6. Johann Heinrich de Graf (Jonny X), was a German communist who was recruited by Soviet Army intelligence, the GRU. He walked into the MI6 station in Berlin to volunteer his services and was run by its head, Frank Foley, who was to become far better known for his work in helping Jews to escape from Nazi Germany. Jonny X had been involved in the organization of the Comintern ‘illegal’ network in Britain and was able to provide vital information not only on the workings of the Comintern but also on its attempts to subvert the governments of Britain, China and Brazil.

  There was often no love lost between MI6 and MI5 during this period, but Curry was full of praise for the ‘close and fruitful collaboration’ on the Comintern. The intelligence from the MI6 agents, and particularly from Jonny X, whom he singled out as ‘very valuable’, was augmented and amplified by the intercepted Comintern messages.

  As Denniston suggested, the Mask operation was also notable as a rare early example of close collaboration between the code-breakers and the Metropolitan Police intercept operators, who during the early 1930s moved to a new location in the grounds of the Metropolitan Police Nursing Home at Denmark Hill, south London. Harold Kenworthy and Leslie Lambert set out to track down the source of the London messages, as they had with the Daily Mail’s transmitter. Since the radio messages were always sent at night, their early attempts to home in on the signal met with suspicion from ordinary police officers and they were handicapped in any explanation by the need to keep what they were doing secret.

  MI6 supplied a van in which they could place the direction-finding equipment while driving around London looking for the transmitter. But Kenworthy recalled that they had to be provided with a special pass after the very act of loading the equipment sparked off a police investigation into an assumed robbery.

  Some exciting moments were experienced – particularly on one occasion, after going round a neighbourhood for some time a police car stopped us. On being asked: “What have you got in that parcel?” – the parcel being a portable short-wave set, Mr Lambert said: “I don’t want to tell you.” After that remark, there was nothing to it but for the pass to be shown. On another occasion, we spotted a PC waiting for us in the middle of a narrow crossing. We literally backed out of this by reversing round a corner and making off in another direction.

  They used a large direction-finding (DF) set in the van to find the general direction and then deployed the portable set to ‘walk in’ on the transmitter. ‘It took a long time to get final results,’ Kenworthy recalled. ‘The search for the unauthorised wireless station went on for some months. We were only one and often after all the preparations the London station would be on the air perhaps two minutes only and then off until the following evening. These chancy sort of conditions made the effort a very long drawn out affair, but it was finally rewarded by locating the station in Wimbledon.’

  An MI5 surveillance operation was then set up. The house was found to belong to Stephen James Wheeton, a Communist Party member. MI5 officers followed him to regular meetings with Alice Holland, a prominent party member, at which the messages were handed over and collected. The transmitter was later moved to north London but it was not long before Kenworthy and Lambert again located it in the home of another party member called William Morrison.

  The Mask operation was inadvertently sabotaged in 1933 when the Moscow station began interfering with a frequency used by the GPO to send telegrams. Since the call sign used by Moscow was similar to those used by the Admiralty for sending diplomatic signals, the GPO rang Henry Maine (the official in charge of liaison with the Post Office to obtain drop copies of enciphered telegrams). The GPO official asked Maine if he knew what station used that particular call sign. ‘He did, and not thinking it necessary to warn them not to take action, told them it was Moscow. The GPO immediately sent a service message to Traffic Controller Moscow Commercial Services to the effect that the transmitter was causing interference to one of their frequencies and would they please shift its frequency.’ Moscow denied any knowledge of the station, Kenworthy said, but it immediately went off the air and did not return for many months. ‘When it did, a completely new system had bee
n devised using more frequencies, numerous call signs and of course an entirely new cipher.’

  This period saw the first co-operation between the British and French codebreakers that was to be so helpful to the later attempts to break the German Enigma machine cipher. Tiltman recalled going to Paris with the then Assistant Chief of MI6, Colonel Stewart Menzies, to meet Colonel Gustave Bertrand, the head of the French codebreaking unit.

  An arrangement had been made for the exchange of information regarding Russian cipher systems between the Government Code and Cypher School and French cryptanalysts. I had worked for 10 years on Russian ciphers, nearly nine years in India, and three years on Comintern ciphers and Commander Denniston, the Director of GC&CS, chose me to go to Paris as having more general knowledge of Russian systems than anyone else in the office (except perhaps Ernst Fetterlein). I flew to Paris on May 24 1933 with General, then Colonel, Stewart Menzies. I spent the whole of May 25 with Bertrand and two other Frenchmen.

  I had been instructed before leaving England that I was not to disclose any knowledge of Russian use of long additives or of one-time pads unless I was satisfied that the French were aware of this usage. I was also told not to discuss Comintern cipher systems at all. It was characteristic of Bertrand as I got to know him later that, immediately after I was introduced to him, he handed me a typewritten statement to the effect that the French were fully aware of the nature of Russian high grade systems. I was therefore free to describe for them the various Russian systems (nearly all diplomatic) I had worked on since joining GC&CS in London in 1920, particularly in India 1921–1929. Much of this was new to them – I don’t remember that they told me anything significant that I didn’t know already.