Secret Life of Bletchley Park - McKay Sinclair [61]
It was a spectacular coup, as Admiral John Godfrey, Director of Naval Intelligence, was keen to tell Bletchley Park. He rang with a message: ‘Tell Dilly that we have won a great victory in the Mediterranean and it is entirely due to him and his girls.’
Mrs Batey illustrates vividly how, when something of vital importance was going on, the codebreakers would not budge until their job was done. ‘Finally,’ she says, ‘the work was finished in the middle of the night after three nights.’
Mrs Batey is modest about her pivotal role. ‘It was the Italians’ errors that gave the game away,’ she says. ‘Our eyes were so used to picking things out. I got a long message and it didn’t have a single “L” in it. The Italians only ever sent out a few telegrams, so the very idea that they were sending messages out automatically gave you the signal that they were going to do something for a change.
‘And so they sent out dummy messages all the time so it would look like a uniform transmission. And of course, what this Italian chap had done was just to sit with his finger on “L”, smoking a fag, the biggest crib there ever was.
‘A message that long that contained only “L”s! That actually broke one of the wheels of the Italian Enigma machine.’
Another 1941 sea battle of some significance to Bletchley took place inside the Arctic Circle, and featured a British attack on German ships. The real target was a trawler called Krebs; for it was known that on board this vessel was an Enigma machine, which could prove invaluable for breaking into those almost impossible German naval codes. The German captain, sensing the danger, threw the Enigma machine overboard into the freezing ocean, but he was killed before he had a chance to destroy his coding documents and bigram tables. The vital documents and tables were retrieved, eventually taken back to Bletchley and pieced together.
Then, even more brilliantly, came the episode of the U-110. This was the U-boat that had, in the first few days of the war, caused widespread public horror by torpedoing and sinking the passenger ship Athenia. Now the U-110 was itself depth-charged and captured in the Atlantic. The captain, Julius Lemp, was unable to prevent the British from seizing vital Enigma material, including bigram tables. These in turn were rushed back to Bletchley. The submarine was being towed to Iceland when it sank; the crew who had torpedoed and drowned so many sailors were now themselves lost. But it was from these courageous naval operations that grew Bletchley’s outstanding achievement – the breaking of the notoriously unbreakable naval Enigma.
Even back in 1940, Alistair Denniston had remarked to Head of Naval Section Frank Birch that ‘You know, the Germans don’t mean you to read their stuff, and I don’t suppose you ever will.’ However, from these tables, and other data, Alan Turing calculated a new method into the codes, which became termed ‘Banburismus’ – in essence, as his Hut 8 colleague and sometime fiancée Joan Murray recalled, it involved ‘punched holes on long sheets of paper, made at Banbury’.
Often on the night shifts, recalled Joan Murray, ‘around midnight was a particularly interesting time, since the German Naval keys changed at midnight, but results of analysis of most of a day’s traffic began to reach us before then.’1 The result, she recalled, was that very often people were too absorbed at the end of the shift – like Mavis Lever – to even think of going home. Instead, they preferred to stay on and carry on working with the following shift.
And the effect it began to have on the course of the war was almost incalculable. In the first few months of 1941, U-boat attacks on the convoys had meant that Britain was facing a catastrophic shortfall of imported food; if the submarines could not be thwarted, there would literally not be enough to feed the population. On top of this, there would not be enough imported