The Bletchley Park Codebreakers (5 page)

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.

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 been 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.

The Mask operation led by Tiltman continued until the middle of 1937. Its significance is confirmed not just by Curry but by Josh Cooper who remarked that while the work carried out by Kenworthy’s police unit was of no particular interest to the police it was ‘of great importance to the future GCHQ’.

Exploitation of Soviet armed forces traffic during the interwar period appears to have been less systematic and therefore less successful than that of the diplomatic and Comintern networks. It is not clear how much military material was deciphered in India. But both Simla and Sarafand had limited success with Russian military ciphers. There was also some early work on the ciphers of the KGB. But during the 1920s and early 1930s, the main focus inside GC&CS with regard to Soviet armed forces was on the Russian Navy.

William ‘Nobby’ Clarke, a former member of Room 40, was one of a number of GC&CS members unhappy at the way in which the codebreakers and the intercept operators were increasingly being asked to work on diplomatic material at the expense of service traffic. He managed to persuade the Admiralty that there should be a naval section within GC&CS and then made the rounds of Royal Navy establishments and ships, coaxing a number of officers into agreeing to intercept Russian, French and Japanese wireless communications in their spare time while at sea. The Royal Navy intercept station at Flowerdown also began taking Russian naval material and the Army station in Sarafand covered the Black Sea Fleet. But the use of one-time pads and a lack of depth ensured that few messages were deciphered.

Clarke’s report on Naval Section work for 1927 admitted that there had been very little naval traffic intercepted, all of it between shore-based establishments. There had, however, been some success in solving a super-enciphered system in which encoded messages were reciphered before transmission, a practice designed to make them more difficult for an eavesdropper to read. The messages were first encoded using a codebook, which provided groups of randomly selected figures for common words or phrases. This produced a series of groups of figures, normally uniformly four-figure or five-figure groups. The operator then took a stream of predetermined but randomly selected figures, placed them underneath his encoded message, and added the two together figure by figure, using non-carrying arithmetic, to produce the reciphered message.

In an attempt to find out whether it was worthwhile continuing to
work on the Russian Navy ciphers, Clarke decided to see the problems faced by his volunteer intercept operators for himself: ‘In the hope of clearing up the problem of Russian naval ciphers, I joined HMS
Curacao
for the Baltic cruise of the 2nd Light Cruiser Squadron … Unfortunately the amount of intercepts available does not permit of much work being undertaken on this kind of traffic nor is it considered that it would be profitable.’ The situation improved slightly in 1929. Although no messages had been broken, enough intercepts were coming in to allow some limited traffic analysis.

During late 1929 and 1930, the Naval Section launched a concerted effort to try to solve the Russian naval codes and ciphers. Josh Cooper was sent to Sarafand to carry out a fifteen-month investigation of Black Sea Fleet communications while Lieutenant-Commander G. A. ‘Titts’ Titterton, a former member of the Naval Section, returned from a Russian interpreter’s course to work on Russian Navy material in London.

Cooper’s report shows that there were a number of different codes and ciphers in use, ranging from relatively simple systems to high-grade ciphers. But while the lower grade systems proved vulnerable he was not able to break any of the high-grade systems and Titterton seems to have had even less success. He left GC&CS briefly in December 1932 and, as one senior codebreaker noted, was replaced by another officer whose ‘skirmish with Russian was also short and unsuccessful’. The lack of success and the need to divert resources to Italian systems as a result of the 1935 Abyssinia Crisis eventually led to Russian Navy coverage being dropped.

But as the attack on Russian Navy systems waned, the Army Section of GC&CS, set up in 1930 under John Tiltman, was beginning to get to grips with an upsurge of Russian Army traffic. This had become available in 1933 as a result of an arrangement with Estonia’s codebreakers, who offered all the material they were intercepting in return for radio equipment. With Tiltman busy, first on the Comintern traffic and later on super-enciphered Japanese army systems, P. K. Fetterlein, the brother of Ernst, was recruited to work on the Estonian material. The creation in 1936 of an Air Section of GC&CS, led by Cooper, gave fresh impetus to this work. Cooper’s experience of Russian material and Tiltman’s preoccupation with Japanese systems appear to have been the main reasons for the Air Section being asked to deal with the Estonian material, since little if
any of it was from Russian Air Force units. ‘The Russian traffic was a mess,’ Cooper said. ‘What we received was a mixed bag from a wide range of stations (some of them in the Leningrad Military District, just over the border, some from at least as far away as the Ukraine), with little or no continuity. Some of the material was in very low-grade systems, which had usually been broken by the Estonians before we got it; the content was of no face value. There was also a variety of higher-grade systems but never enough of any one line to make a crypt attack possible. Controlled interception of selected lines of traffic with good T/A backup might at this time have produced very interesting results, but we could not control the Estonians.’

By 1938, with war against Germany beginning to look inevitable, the main priority had become the breaking of the German Enigma machine cipher, although Russia still remained high on the GC&CS list of target countries. Lieutenant-Commander Titterton had now returned to Broadway and the Home Fleet had resumed interception of Russian Navy traffic. As late as mid-1938, two new junior assistants were recruited solely for their knowledge of Russian, one of them being Alexis Vlasto, whose
A Linguistic History of Russia to the End of the Eighteenth Century
remains a standard textbook. Russia also remained a high priority in India, where the codebreakers had broken the Soviet secret service super-enciphered code.

The responsibility for the Russian material was subsequently handed back to the military section, together with the services of P. K. Fetterlein. The 1939 co-operation with the Polish and French codebreakers, that was to be of immense importance in the breaking of the German Enigma machine cipher, had the added bonus of providing a batch of material from Lithuanian and Latvian codebreakers, Cooper recalled. ‘The raw material was similar in quality to the Estonian and work on this untidy mass of miscellaneous Soviet services was co-ordinated in the Military Section with Vlasto as Air Section’s contribution. There was only one consignment of Lithuanian and Latvian. Estonian went on, I think, for a while with deliveries by diplomatic bag.’

By now, the codebreakers had been moved out of London to the MI6 ‘War Station’ at Bletchley Park, designated Station X. This was not, as is sometimes supposed, a mark of mystery, but simply because it was the tenth in a number of properties acquired by MI6, all of which were designated using Roman numerals. The number of staff remained limited – only 137 of those who went to Bletchley in August
1939 were members of the GC&CS codebreaking sections. But the alliance between Stalin and Hitler continued to ensure that Russian material retained a high priority. Co-operation with the French was expanded. A dedicated Russian section was set up under Tiltman’s tutelage at Wavendon, a country house close to Bletchley Park, and another Russian section was set up at Sarafand, in Palestine.

The crucial breakthrough on Russian armed forces material came during the Russo-Finnish War in late 1939 and early 1940. The large amount of traffic created by the Russian Army’s invasion of Finland, and the Finns’ determined defence of their territory, gave the codebreakers enough depth to solve two high-grade Russian systems: the Soviet Army’s GKK super-enciphered code and the OKF super-enciphered naval code.

It is not clear who made the break into the two Russian high-grade systems, but it seems likely that Tiltman was yet again involved. He was in charge of the section, had worked on a number of similar Japanese Army systems and, the previous year, had broken the Japanese Navy’s main super-enciphered code, known to the Allies as JN-25, within weeks of its introduction. It was also Tiltman who set up an arrangement with the Finnish Army’s codebreaking unit in order to obtain as much of the Russian traffic as possible to allow further recovery of the system. ‘He had the foresight to note the extreme importance of Finnish collaboration in our Russian work,’ Denniston said. ‘He spent a fortnight in Finland and established a close and friendly liaison with their cryptographic unit and his persistent drive … may well seal an alliance which should prove of the greatest value to the intelligence departments of all three services.’