The Secrets of Station X by Michael Smith Page A

against each other, nor eaten so much Brie in so short a time.’
    Turing had spent his time since arriving in the Cottage working on Naval Enigma, which Knox had put to one side since it was a more difficult problem than German Army and Luftwaffe Enigma. He had also been busy devising a machine, called the Bombe, after the Bomby , although it was a morecomplex piece of equipment than its Polish namesake. This would test the encyphered messages against commonly used streams of text – known to the codebreakers as cribs – to narrow down the possibilities for the keys, settings and wheel orders of the Enigma machines. Turing enjoyed a good degree of progress on both. Menzies agreed funding of £100,000 for the construction of the first Bombes and the British Tabulating Machinery company (BTM) was commissioned to build it, with the work supervised by the BTM research director Harold ‘Doc’ Keen. Then in December 1939, Turing managed to work out the indicator systems for five days of pre-war Naval Enigma traffic. But neither the Poles in France nor the British could manage to break a wartime Enigma message. Dennis Babbage, one of the young mathematicians who had joined the small party in the cottage, recalled that attacks were made on numerous days’ traffic. ‘One after the other they went down and a general gloom descended.’
    This period was not entirely wasted because the codebreakers discovered one feature of the way in which the ordinary signals operators set up the machine. The operators were using pronounceable sequences of letters for the three-letter message settings on the machine, these were usually the first three letters of a word, or their girlfriends’ names, sometimes even the first three letters of obscenities. They became known as Cillies because one of the first that was spotted was CIL, an abbreviated form of the German girl’s name Cilli. ‘Just occasionally you would get a chap who was rather fond of the same letters,’ said Susan Wenham, who was twenty-eight and one of the young female codebreakers recruited from Newnham College, Cambridge. ‘It might be for some personal reason. Perhaps one chap might use his girlfriend’s initials for the setting of the wheels or his own initials. Something like that, you know, silly little things. They weren’t supposed to do it but they did.’ Searching for Cillies became something of an art, said Mavis Lever, another of the young female codebreakers, who also worked on four-wheeledEnigmas. ‘One was thinking all the time about the psychology of what it was like in the middle of the fighting when you were supposed to be encoding a message for your general and you had to put three or four letters in these little windows and in the heat of the battle you would put up your girlfriend’s name or dirty four-letter German words. I am the world’s expert on dirty German four-letter words!’
    But no actual cyphers were being broken and the pressure got to Knox, who had just been appointed Chief Assistant, effectively the chief cryptographer. He threatened to resign, an approach he was prone to take when he felt the battle to break the cyphers was not being pursued with sufficient vigour by those in charge. At the Pyry conference, he and Denniston had promised to send the Poles more of the Zygalski sheets, which they had been unable to procure. These had been produced, but never sent. In a letter to Denniston, Knox insisted that the Zygalski sheets must be taken to the Poles in France immediately. ‘My personal feelings on the matter are so strong that unless they leave by Wednesday night I shall tender my resignation,’ he said. ‘I do not want to go to Paris but if you cannot secure another messenger I’m actually at the moment completely idle.’
    In fact, Turing was sent to Mission Richard with the Zygalski sheets and a brief to find out why the codebreakers were unable to