Alastair Denniston

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

  By the mid-1920s, GC&CS staff numbered twenty-five officers (one head, six senior assistants, eighteen junior assistants) and about twentyeight clerical staff (six typists, twelve clerks for code construction and ten traffic sorters and slip readers36). AGD began recruiting staff from the universities as early as 1925. Initially, those brought in were classicists, linguists and papyrologists, and the establishment increased to ten seniors and twenty juniors. As there was virtually no difference between the work of good juniors and seniors, in the early 1930s the balance was changed to fifteen seniors and fifteen juniors. The services also contributed staff and from 1923, the Admiralty’s interest in Japanese diplomatic and naval attaché traffic led to the permanent placing of a Japanese interpreter officer in GC&CS.

  The War Office established a station at Sarafand in Palestine, with an intercepting and cryptographic unit which had close links to GC&CS. In November 1925 AGD visited Sarafand to research the setting-up of wireless stations there. He arrived on 7 November and wrote to Dorothy every few days. ‘Y’ was almost six months old and AGD was clearly missing his family, ending one letter ‘Good night dearest D.G. & kiss wee Y on the brow for me’. He carefully restricted himself to general descriptions of life in the areas he visited. While much of his time was spent travelling to potential wireless station sites in Egypt and Palestine, he still managed to fit in the odd game of tennis and round of golf. He boarded a ship, the Maloja, on Sunday, 22 November, at Port Said and arrived in Marseilles on Friday, 27 November. He then took the train to Paris and the boat train from Calais, arriving home the following day.

  The War Office also sent officers to GC&CS for training before being posted abroad. Pre-eminent amongst these was John Tiltman,37 who would remain a close friend of AGD for the rest of his life. Older specialists were drawn from the original Room 40/MI1(b) staff, such as Ernest Hobart-Hampden, former consul in China and Japan, and Ernst Fetterlein,38 a former Tsarist cryptanalyst.

  On 29 July 1926, AGD’s deputy, Edward Travis, in his role of protecting British codes and cyphers, received a note from R. Hume, probably from the embassy in Berlin. The Admiralty wished to purchase two Enigma encryption machines which were commercially available in Germany. Hume informed Travis that a new machine was under development which was cheaper, simpler and more fool-proof, although not available for ten months. The existing large machines cost 2,000 marks (less than £100) while the smaller machine was 600 marks (less than £30). Travis replied by telegram in September, saying ‘Am proceeding Prague to inspect machine for War Office. Admiralty wish me to break journey at Berlin and ascertain particulars of new Enigma.’ Travis duly travelled to Berlin and purchased one machine for the British Government and brought it back to London.39 It survives to this day and is on display in alternate years at Bletchley Park and GCHQ.

  The Armistice which marked the cessation of hostilities on the Western Front had seen the end of military wireless traffic. This had enabled Lord Curzon to argue successfully for the move of GC&CS to the Foreign Office. Over the following years, the focus of AGD’s organisation was very much on diplomatic traffic. Some elementary work had been carried out from 1914–18 by both Room 40 and MI1(b). AGD had taken a small Admiralty party to Paris in April 1919 to work with the French on German material during the Peace Conference and stayed until the signing of the Peace of Versailles. He regarded the trip as ‘useless though pleasant’, the latter because the party included Dorothy.40 The Germans came to the conference with new code books and methods, not surprisingly following the Zimmermann Telegram episode. In 1919, only a small number of staff had any real cryptography expertise and most were linguists. The reconstruction of code books being used by various governments and the translation and editing of the resulting text was GC&CS’s primary function in the early years of its existence. Fetterlein, Strachey and Knox were the key men initially, along with Turner as master-linguist and Hobart-Hampden in charge of Japanese work.

  Code books, known as ‘hat books’, were used by the Germans and within one year of GC&CS’s inception, they could be solved by one good linguist. The work was based on a method used by Ernst Fetterlein for many years in this type of work in Russia. John Tiltman joined Fetterlein’s team in the summer of 1920 and later recalled their work:

  I worked as one of a group of from 5 to 7 persons on Russian diplomatic ciphers under the direction of Ernst Fetterlein. Fetterlein had been Chief Cryptanalyst of the Russian Czarist Government and held the rank of both admiral and general; he had practiced cryptanalysis since 1898 or earlier. At the Revolution he walked out of Russia across the Finnish frontier and was specially naturalized on arrival in England.

  At the time of my arrival, Fetterlein’s small section was entirely occupied with the solution of the current Moscow-London and London-Moscow diplomatic traffic intercepted in the cable office. All messages were enciphered by simple columnar transposition of Russian plain text conventionally transliterated out of Cyrillic characters, As each message was transposed on a different key, all messages had to be individually solved. The average delay, was I believe, 1 or 2 days. 41

  The traffic of two British allies was also read, as AGD recalled:

  The Americans celebrated the advent of peace by introducing a new hatted diplomatic code recyphered with tables changing quarterly. The solution of the first of these tables was a year’s work and thereafter the American Section had to be expanded for the increased task of breaking the tables and reconstructing the code. Good progress was made and the section was able to be of some assistance during the Washington Naval Conference of 1922.

  The second really big task was to make a concentrated attack on French Diplomatic cyphers, which had received no attention during the war.

  A large number of hatted books of 10,000 groups were used and with the constant practice of reconstruction of such books they never presented any difficulty. Given sufficient traffic, legibility appeared with a month of birth. Many recycled books also appeared and after the initial struggle to obtain the general system the constant change of tables presented little difficulty.

  The reading of this traffic during the years of peace and intrigue did from time to time produce very interesting if not invaluable intelligence. But the proximity of the two capitals did mean that a great deal passed by bag.42

  Only the Soviet traffic yielded operational intelligence. According to AGD:

  The Revolutionary Government in 1919 had no codes and did not risk using the Czarist codes which they must have inherited. They began with simple transposition of plain Russian and gradually developed systems of increasing difficulty. The presence of Fetterlein as a senior member of the staff and two very competent girls, refugees from Russia, with a perfect knowledge of the language, who subsequently became permanent members of the staff, enabled us to succeed in this work. We were also able to borrow certain British Consuls who could not return to Russia.43

  A major effort was made on Japanese diplomatic traffic and was largely productive. It was led by Hobart-Hampden who had thirty years of service in Asia. While no more than 20 per cent of the intercepted traffic was read and circulated, the Section was able to provide the views of the Japanese Government in advance of major conferences. Hobart-Hamden was joined by another former member of the British service in Japan, Sir Harold Parlett, in 1926.

  A watch was kept on all former enemy countries, and it was known that Germany was using OTPs and a second method nicknamed ‘Floradora’, which was eventually broken during WW2. Austrian traffic was read in 1918–19, thanks to work by Fetterlein. Knox successfully read some Hungarian traffic and, building on work in MI1(b) and Room 40, traffic was read from Greece, Spain, Italy, Scandinavia and Persia. Targets were driven by the politics of the day so new sections looked at various South American republics, Portugal, Brazil, the Balkans and Near East.

  AGD summarised GC&CS’s effort on diplomatic traffic over its first twenty years as follows:

  To sum up the cryptographic effort of twent
y years on diplomatic traffic: we started in 1919 at the period of bow-and-arrow methods, i.e., alphabetic books; we followed the various developments of security measures adopted in every country; we reached 1939 with a full knowledge of all of the methods evolved, and with the ability to read all diplomatic communications of all powers except those which had been forced, like Germany and Russia, to adopt OTP.

  The authority who sanctioned our Establishment in 1919 clearly never envisaged a complete reading, translation and issue of every telegram received by us.

  Such was a physical impossibility for the thirty specialists who composed the main body of the staff employed on the work.

  Hence from the outset sections did exercise their own discretion as to what they translated and submitted for circulation. They got guidance from the D and R who in turn received intelligence directives from the Foreign Office, the circulating sections of SIS and the officers who used our material in the Service and other large departments.

  During the thirties we did supplement our daily issue by a daily ‘Summary of telegrams decoded but not circulated’, for the benefit of SIS, Admiralty and War Office (occasionally the Foreign Office) and it is noteworthy that it was only a very small percentage that were ever asked for in complete form.

  With personal satisfaction I maintain that GC and CS did during those twenty years fulfil its allotted function with success, with exiguous numbers and with an absence of publicity which greatly enhanced the value of its work.44

  Apart from the diplomatic traffic, unusual transmissions were picked up around 1930 which turned out to be a worldwide network of clandestine stations controlled by a station near Moscow (the Comintern network). The police station at Denmark Hill45 in South London obtained German diplomatic traffic broadcasts in 1937–8 from an unlisted station in Germany to unknown recipient call signs as well as obvious replies from unknown stations. Interception, traffic analysis and direction finding helped in these early days to map the traffic between German embassies, legations and consulates.

  GC&CS had no W/T intercept facilities of its own and was totally dependent on the Admiralty and War Office for material to work on. Sinclair had persuaded the Admiralty to retain its intercept stations at Scarborough and Pembroke at the end of WW1. The Military Directorate in the War Office had also agreed to retain its station at Chatham. While there was little German naval traffic in the early 1920s due to the fact that Germany had no real navy, GC&CS’s Naval Section was probably set up in 1921 when Clarke joined after completing a naval history of WW1. What German naval traffic there was could not be read and, by the mid-1920s, this could well have been early Enigma traffic. Italy did have a navy, however, and its traffic was read by reconstructing their main naval code book. This work was helped by the Italians’ habit of enciphering long political leaders from the daily press. Around 1934, Italian naval traffic increased, albeit in a more secure form, so GC&CS’s naval Italian section continued to grow to keep pace with it. Their reports kept DNI well informed about Italian naval plans. During the Spanish Civil War between 1936 and 1939, the Italians introduced the commercial Enigma machine for all of their secret naval communications. Hitler had issued an order for ten Enigma machines to be sent to Franco in October 1936, so it is likely that some were also provided to Mussolini at the same time. This gave GC&CS and a team led by Knox and including William Bodsworth, its first opportunity to research machine encryption. This pioneering work would prove invaluable in the years to come and it was Bodsworth who broke Enigma traffic between Franco’s navy and the Italian Navy, the Regia Marina, in late April 1937.46 By 1936, a large amount of German naval traffic started to appear in the Mediterranean. Knox made some progress but by 1937 the security of the German naval Enigma machine had been significantly enhanced with an attachment known as the steckerboard.47 The Germans also added code books as part of the daily Enigma setup procedure and Knox made no further progress. The only source of intelligence came from an early form of traffic analysis which looked at the origins of traffic and plotted the routes that it followed.

  A start was also made on Japanese naval traffic, and while there was no interception in Britain, a steady flow of material was delivered by bag to London. A small bureau for interception and cryptography was established, initially in Hong Kong and then Singapore in 1939. AGD summarised the situation in 1939 as follows: ‘To sum up the situation of the Naval Section in 1939, including the Japanese branch in Hong Kong: they exercised a very fair measure of control of all Italian and Japanese naval cyphers; they had only seen German signals by the Enigma machine and this they could not read; they had started an intensive professional study of raw German traffic with a view to extracting any available intelligence.’

  Many of the foundations of a united Sigint Service were laid in the post-WW1 arrangements, but the Service Ministries seemed to regard them as peacetime arrangements only. War Office policy was summarised in 1925 as follows:

  On the outbreak of war the War Office will be responsible for intercepting the enemy’s field wireless sets, and for collecting all information obtainable from this source. For this purpose it will provide, from officers on the active list and on the reserve, the necessary personnel for wireless intelligence and cryptography.

  At this stage the help of the GC&CS will only be required in the event of the enemy using a cypher which cannot be broken by the cryptographers in the field. Should this occur the GC&CS will be provided with the necessary material and asked to break the cypher. When this has been done, the results will be handed over to the cryptographers in the field who will thenceforth decipher the messages.48

  The Navy also intended to run its own ‘show’, and as the DNI wrote in November 1927: ‘On the outbreak of war, the entire naval section of the Government Code and Cypher School will be transferred to the Admiralty, who may require it to go abroad. This transfer may be called for in an emergency other than war, and the Admiralty will always decide when the transfer is necessary. The naval section will then come entirely under the orders of the Admiralty.’49

  The RAF was still happy, in the event of offensive warfare abroad, to ‘obtain its intelligence either from the Army or Navy, therefore GC&CS needs take no steps in this matter’. It assumed that it was responsible for erecting W/T and direction finding (D/F) stations to locate enemy aircraft and that: ‘The best solution [to the cryptanalytic problem] would be for the Air Force to possess a small nucleus of officers who had received training in simple cryptography. These trained Air Force officers would be attached on the outbreak of a European war to Air Defence headquarters, and they could be reinforced, if necessary, either by one or two members of the GC&CS or by the recruits called up by the GC&CS.’50 The higher authorities in the RAF had no WW1 Sigint experience and as AGD wrote in 1932 ‘the higher authorities were frankly very sceptical about the value of wireless interception and intelligence obtained therefrom’.51 In 1927, following recommendations by the Romer Committee in 1924, an Air Ministry Y station was erected near Waddington. Initially dealing with diplomatic traffic, by 1932 it was processing enough Russian air material to appoint a cryptanalyst and when he died in 1934, two others were appointed and stationed with GC&CS. In 1936, with the threat of war looming, the Air Ministry intelligence authorities felt that they needed their own experts, so a cryptanalytic Air Section was attached to GC&CS under J.E.S. (Josh) Cooper. He had been a member of GC&CS since 1925 and was transferred from the Foreign Office to the Air Ministry Civil Establishment. By 1938, the section had been expanded and Waddington transferred to Chatham to provided foreign air traffic to GC&CS. The RAF also recruited a former Royal Signals NCO who was promised a commission. A station was set up at Mere Branston and then moved to Cheadle in 1937.

  The Army opened a Y station at Fort Bridgewoods, Chatham in 1926 and made progress thanks to Lieutenant-Commander (later Lieutenant-Colonel) M.J.W. Ellingworth. The War Office had been sending serving Army officers to GC&CS for training ever since GC&CS was formed, but this
resulted in the Military Wing in GC&CS not being as cohesive as its Naval and RAF counterparts.

  A separate GC&CS Military Section was not set up until after 1930. It was established under Tiltman, although he remained on the payroll of the War Office. F.A. Jacobs, a recently retired Army captain, joined him as deputy along with eight staff, including at least two civilian cryptanalysts. Experience had modified War Office policy and all Sigint stations overseas were not regarded as being under the control of AGD and the Committee. Furthermore, ‘the GC&CS should be responsible for the control of the interception of traffic by permanent stations, and the War Office for expeditionary force traffic’. Also ‘the War Office would certainly require a section of GC&CS to continue foreign military intelligence as well as a cryptographic staff with the expeditionary force’.52

  Military Intelligence had maintained an interest in interception and cryptography, which is why they sent officers to GC&CS for training. The Admiralty would lend officers to GC&CS to assist in producing results. The War Office had maintained posts abroad and set up a permanent intercept station in the Middle East in the early 1920s and in 1923 at Sarafand, with three officers attached to No. 2 W/T Company there. GC&CS’s Military Section worked closely with the intercept station at Chatham, which produced the first army and air force material and German police transmissions in 1937. Knox led the attack on the German military Enigma, having failed to make progress on their naval Enigma traffic.