Alastair Denniston

by Alastair Denniston- Code-breaking From Room 40 to Berkeley Street

  Commercial work was not in the original GC&CS mandate but in 1938, Sinclair and DNI agreed that in the event of political turmoil in the Far East, the Japanese might enhance the security of their diplomatic and service traffic. Therefore, the communications of large Japanese companies might provide useful intelligence. A small section was set up under Hope in 1938 to investigate commercial traffic, telegrams of large Japanese firms, less likely to be enciphered than Japanese diplomatic and service material.

  While initially set up as a ‘School’ to study world-wide cryptographic methods and practices, events led GC&CS to develop a dual role as a Sigint ‘Centre’, tasked with extracting as much intelligence as possible, as quickly as possible from communications which were of interest to the British Government and relevant departments. The original sanctioned staff consisted of twenty-five cryptanalysts and around thirty support staff. As many as ten Service officers were loaned to GC&CS until the Military and Air Sections were established. Clearly, the size of GC&CS meant that it could not cover all of the diplomatic and commercial traffic circulating around the world. AGD, as Head was responsible for allocating tasks, directing all branches of work and line managing all subordinate Section Heads. This remained the model for diplomatic work both between the wars and during WW2. He had a registry for correspondence and a small number of administration staff. Travis, as his deputy, was responsible for advising on the security of British codes and ciphers and assisting on their provision. He was eventually assigned a junior assistant and clerical staff which formed the nucleus of the Cipher Security Department. On 2 January 1933, AGD received another honour in his capacity as the head of a department of the Foreign Office. He was appointed a Companion of the Order of the British Empire (CBE).

  Diplomatic ‘product’ did not require much comment or interpretation. It was processed by a Distribution and Reference Section which was led by a senior officer with cryptanalytic expertise. The section became a reference library which was indexed for research and editorial ease. It never exceeded five staff, including support staff. Unlike the rest of GC&CS, which allocated tasks to a team of cryptanalysts, the Diplomatic Section assigned tasks to one senior cryptanalyst who possessed wide linguistic expertise, thus bypassing the ‘country section’ organisation which was in place. This suited the ‘country section’ model of flexibility and variability of size. For example, during the Italian-Ethiopian War in 1935–6, Italian diplomatic traffic could be exploited so the Italian Section was increased from five to twenty. This was done by passing the work to experienced cryptanalysts and their support staff in other sections such as the French, Romanian and Scandinavian.

  In the early days of GC&CS, several experienced cryptanalysts with mathematical expertise were used on more difficult problems such as the German OTP or when a country section was unable to make progress. A senior linguist was also employed in this way and these men reported directly to AGD. At that time there were a number of small country sections, including French, Belgian, Japanese, Italian, Spanish, Near Eastern, Balkan States, Scandinavia and Greek. Not all countries could be covered due to a shortage of staff. The Heads of all of these country sections reported to AGD. The Head of each section selected which deciphered material should be translated and submitted for circulation. The Distribution and Reference Section, by its contacts with the user departments, became the conveyer to the country sections of current priorities; and its Head, by continuity of experience and knowledge of current needs, had become a guide to the exploiting sections in this matter. No more formal ‘priorities’ machinery existed. During the Ethiopian and Spanish Civil wars, the Diplomatic Sections gained valuable experience about the value of its product in supporting military, naval and air operations. It also realised that standard commercial coded traffic might be of considerable value to ‘Economic Warfare’. In 1938, a special Commercial Section’ was set up. Therefore, the Diplomatic and Commercial Sections were already operational and experienced in their work at the beginning of WW2. While the organisation would have to expand to provide full cover as required by their ‘customers’, they would never face the expansion, evolution and exploitation problems faced by the Service Sections. It was able to retain its pre-war structure throughout the war.

  GC&CS continued to deal with Japan’s diplomatic and naval attaché communications which could be intercepted at home. Consular, military and naval traffic was handled by outstations in the Far East. Copies of translations were sent to DNI and intercepts to GC&CS, which used them as training material or for cryptanalysis on unbroken systems. There was an agreement between DNI and AGD that in the event of war, GC&CS’s Naval Section would transfer to the Far East theatre.53 A Far Eastern Bureau was considered necessary and it would be interservice in nature. In the Spring of 1934, the bureau was set up on Stonecutters Island in Hong Kong. By June 1935, it was completely staffed and while intelligence was handled on an inter-service basis, apart from five RAF staff the cryptanalysts and interception staff were from the Navy.54 From 1935 to 1939 there was a shift in Sigint concern from the Far East to the Middle East and from the Mediterranean to Western Europe. There was still no Army or RAF presence at the Hong Kong Bureau (Hong Kong Combined Bureau or Far East Combined Bureau [FECB]). The Army was waiting for preliminary cryptanalytical research in the Military Section of GC&CS to facilitate local exploitation. By 1939, progress at GC&CS was sufficient for two Army officers and one RAF officer to be sent to FECB. Up until 1938, GC&CS’s Naval Section and the FECB were successful in reading Japan’s diplomatic and naval attaché machine cipher. FECB reported being able to be ‘in the happy position of being able to read all Japanese Naval cypher messages’.55At the end of 1938, Japan rapidly changed its cryptographic systems. Its fleet introduced a five-figure subtractor cipher56, while diplomatic and consular traffic used a new electrical cipher machine, called the ‘Purple Machine’ by the Americans. Little progress was made against the Japanese fleet system, called JN25, by FECB staff, but it was broken by Tiltman (he had made the earlier break into the main military cipher) and the first decrypted messages were dispatched to FECB in September 1939. By then plans were in place to move FECB to Singapore. GC&CS had provided FECB with JN25 codebreaking material in September 1939, which was used on 75 per cent of Japanese naval traffic. However, GC&CS made virtually no contribution to anti-Japanese Service Sigint from 3 September 1939 until the outbreak of war with Japan in December 1941. The Japanese Diplomatic Subsection translated and did minor research on Japanese diplomatic ciphers.

  In early 1934, Italian naval Sigint became of interest as Italy seemed to be on a war footing and communications contained operational intelligence. By the end of 1937, GC&CS’s Naval Section (eighteen strong excluding Japanese staff)) was engaged almost entirely on Italian Sigint. Encrypted traffic was provided by intercept stations at Flowerdown, Malta and Gibraltar. The Military Section was also concentrating on Italian work by 1936, with seven officers involved, supported by six female clerks. By 1938, with six current Italian code books and much of the traffic being read, Tiltman complained about the lack of resources. Encrypted traffic was provided by the intercept station at Chatham and abroad from Sarafand in Palestine and detachments from there. Tiltman’s section also tackled Italian air ciphers.

  The Air Ministry was finally stirred into action with the resurgence of the German Air Force (GAF) in 1935, and a section, A.I.1e, was formed to scan, translate and summarise plain text intercepts. In July 1938, it was suggested to AGD that coordination could best be achieved in Malta by a small inter-service Y Intelligence Centre in which intelligence officers from the three Services would produce intelligence from intercepts, direction finding bearings and ciphers broken in GC&CS. AGD proposed the creation of a Combined Bureau in the Middle East, similar to FECB, to perform all Sigint functions, including cryptanalysis. Each Service favoured its own main station: Malta for the Navy, Sarafand for the Army and Cairo for the Air Force. In the end a Middle East Intelligence Centre was set up in Cai
ro in the summer of 1939, receiving decrypts direct from Sarafand and via the War Office, from GC&CS. NID got Board approval for an Operations Intelligence Centre in Malta and AGD reluctantly agreed in July 1939 to supply, for local exploitation, ‘any broken cyphers used unrecyphered by the Italians since such books can be used without the assistance of a skilled cryptographic staff’.57

  In May 1938, a German subsection of the Naval Section at GC&CS was set up to analyse traffic, consisting of one officer and one lady clerk. However, German military W/T activity was suspended at Chatham in 1935. The study of German Army systems did not even rate a mention in the Military Section report of July 1938.58 Even though the Air Ministry was aware of the growth of GAF activity in 1935, it was a low priority of the Air Section in 1936 59 and Italian traffic remained its main concern.

  The general view within the British Service and intelligence communities in the mid- to late 1930s was that the likelihood of solving Enigma was ‘not yet sufficient to justify real confidence in eventual success’.60 German diplomatic traffic was unreadable, and even lowlevel German Army transposition and stencil systems had not been broken and no effort was being made on naval Enigma until military Enigma was solved. The Air Ministry believed that Enigma was not being used by the GAF. AGD himself seemed to be pessimistic ‘as to the possible value of cryptography in another war’61 and Sinclair was concerned after the Munich crisis ‘that as soon as matters become serious, wireless silence is enforced, and that therefore this organisation of ours is useless for the purpose for which it is intended’.62 The Naval Section of GC&CS wrote to AGD in February 1938 saying that ‘D/F will certainly be our only real source of information as to enemy movements by sea, land and air in the early and therefore probably the most important days of a modern war’.63 However, Service Ministry thinking was starting to change and, increasingly, their view was that in the event of war, the Sigint effort shouldn’t be split between them. The Main Committee recommended the interconnection of all intercept and D/F stations in the UK to GC&CS by telephone and teleprinter and the formation of a ‘joint Inter-Service Operational Intelligence Section at the GC&CS’.64 But the Ministries preferred to keep ‘operational intelligence’ under their control and the section was never formed. However, it did speed up the expansion and improvement of D/F facilities and the communications needed to combine the stations into a network. All Y stations were linked to GC&CS and a Defence Services Lines Telecommunications Board (DSLTB) created by the Director-General of the Post Office, with representatives of all Services and AGD. The teleprinter and telephone lines converged on a special room at the Central Telegraph Office (CTO) in London, which was connected by a private cable to GC&CS in the Broadway Buildings, to operate the system from another centre such as GC&CS’s war station at BP. It was only necessary to switch the system over from the CTO room to the new site.

  The RAF needed Sigint to be delivered swiftly and a test was carried out in March 1938 to demonstrate the advantages of decentralised cryptanalysis. Italian and Spanish Nationalist Air Force traffic was sent to Waddington where Cooper and two other cryptanalysts, supported by a colleague at GC&CS, spent three days decrypting and reporting on the traffic. This convinced the Air Ministry that a cryptanalysis section should be located at the central Y station in peace or war. The role of the GC&CS Air Section would be restricted to cryptanalysis and training new personnel. Meanwhile, the Admiralty set up an Operational Intelligence Centre in 1937, but Operational Intelligence was another name for traffic analysis which was really carried out in the Naval Section of GC&CS. The new centre collated intelligence from non-Sigint sources or decrypts from GC&CS.

  By 1938, it was increasingly clear to AGD that he was going to have to expand his organisation. With Sinclair’s backing, he asked two former Cambridge dons, Frank Birch and Frank Adcock, both veterans of WW1 codebreaking, to trawl through the staff and student lists at both Oxford and Cambridge and other universities. They were looking for men who were deemed suitable for secret intelligence work within the Foreign Office. While the WW1 cryptanalysts did not have much time for mathematicians, GC&CS had recruited one before 1935 and was already putting a Cambridge mathematician through preliminary training in London. A second was recruited from Oxford in February 1939. Through the Chief Clerk’s Department, AGD got the Treasury to sanction fifty-six senior assistants at £600 per year and thirty women with a graduate’s knowledge of at least two of the languages required at £3 per week.

  According to AGD: ‘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.’65 One such recruit was E.R.P. Vincent, a Fellow of Corpus Christi and a professor of Italian. He had learned German during his internment in Germany during WW1. He later recalled dinner with Adcock in the spring of 1937:

  We dined very well, for he was something of an epicure, and the meal was very suitably concluded with a bottle of 1920 port. It was then that he did something which seemed to me most extraordinary; he went quickly to the door, looked outside and then came back to his seat. As a reader of spy fiction I recognised the procedure, but I never expected to witness it. He then told me that he was authorised to offer me a post in an organisation working under the Foreign Office, but which was so secret he couldn’t tell me anything about it. I thought that if that was the case he need not have been so cautious about eavesdropping, but I didn’t say so. He told me that war with Germany was inevitable and that it would be an advantage for one of my qualifications to prepare to have something useful to do.66

  Vincent was summoned by telephone to Broadway Buildings in London shortly afterwards and returned periodically until war was declared. He was able to learn something about cryptographic problems and he ‘picked up the jargon and got to know some of the people’.

  Another recruit in 1938 would certainly make his mark during the impending war. Alan Turing was identified by either Adcock or Birch as having the right skills for GC&CS and he was invited to a training course at GC&CS’s offices in London in the summer of 1938. He attended another course at Christmas and then visited every two or three weeks to help with the work. He was attached to a team led by Dilly Knox and worked alongside Peter Twinn,67 the young mathematician who had been recruited from Oxford in February 1939.

  Throughout the 1930s, Sinclair had become concerned that his intelligence organisations were based in Central London, which would make them vulnerable in the event of war. He started to look for somewhere outside of London to establish a war station for intelligence activities. In early 1937, it was brought to his attention that the remains of a large Victorian estate, located around 50 miles from London, was on the market.68 Its 55 acres would provide ample space for a growing intelligence organisation. Furthermore, it was only five minutes’ walk to a railway station, which sat on the main line from London to the North. Also close by was the main north/south arterial road. Sinclair initially leased the property and, on 9 June 1938, he purchased the property, called Bletchley Park, for £6,000. This was done using his own initiative and many authors believe that he was following a Service tradition by paying for it out of his own pocket. The Official History of MI6 is less certain:

  The relevant property transaction documents show him personally as the sole owner, and after he died in November 1939, apart from legacies of £3,500 to each of his two sons, his sister Evelyn inherited the remainder of his property, with a total value of £21,391. In April 1940 Evelyn (as personal representative of ‘Sir Hugh Sinclair deceased’) transferred BP to William Ridley and Percy Stanley Sykes [the Service’s Finance Officer] for ten shillings [40p]. In their turn, on 3 March 1947, Ridley and Sykes transferred the property to the Ministry of Works, again for ten shillings, all of which strongly suggests that the original purchase money had come from public, if not also SIS, funds.
69

  Engineers from the GPO began installing telecommunications equipment and by the autumn, enough was in place for Sinclair to order a dress rehearsal at his new intelligence war station. As the Head of GC&CS’s Air Section, Josh Cooper, remembered:

  In Autumn 1938 GC&CS had no administrative staff and the Admiral (who appears to have taken the decision to move unilaterally) put Captain Ridley RN of SIS in charge. All personnel of every grade were accommodated in hotels in Bletchley and surrounding towns and villages. The Admiral sent out an excellent chef from London and we all sat down to lunch together at one long table in the House. All this was simply paid for out of SIS funds; Captain Ridley was not concerned with Civil Service regulations. A large room on the ground floor of the House had been set aside for Air Section. Tables and chairs had been provided but there were no cupboards and I remember coming into a scene of chaos with a great mound of books and papers piled on the floor. After Munich we all trooped back to London.70

  The rehearsal at BP revealed a number of shortcomings in accommodation (work and billeting), in staff and in efficiency of communication. So while GC&CS staff returned to London after the signing of the Munich Agreement71 on 30 September 1938, work continued on preparing BP for war and improving arrangements for accommodation and catering.

  By the end of 1938, the Air Ministry not only recognised its responsibility for the air defence of Britain, but also that it couldn’t live off the work of other Services. A Section at GC&CS would have to be engaged in cryptanalytic research and training and would work with a W/T and direction finding complex centred at Cheadle. For the War Office, MI8 would take over Sigint responsibility in September 1939 and ‘the collection, correlation and dissemination of all Military Intelligence obtained from the study of foreign military intercepted communications, for the plotting and identification of foreign enemy wireless stations, the breaking of foreign code call systems and the measure of the enemy’s wireless activity’.72 Chatham was concerned with purely strategic interception work and the Military section of GC&CS, like its Air Force counterpart, with higher-grade cryptanalysis and training. At this stage, the Air Ministry was concerned about the defence of Britain and had made no provision for strategic interception, on the basis that there was no such traffic. The War Office was concerned with Sigint in the field and their Chatham Y station alone intercepted GAF Enigma traffic. The Army and Air Ministries controlled their respective sections at GC&CS, while the Admiralty did not, following the removal of its GC &CS’s sections operational intelligence work.