The Bletchley Park Codebreakers by Michael Smith Read Free Book Online Page A

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 thePost 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.
    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