Someone told me yesterday that the last cryptographer from Bletchley park had died, and I said that can't be true: my mother's still alive. She's 96 and her memory is not wholly reliable – besides, she spent the best part of 40 years after the war forgetting what she had done there, since that was the easiest way not to talk about it. I believe she wrote a history of her section that was never intended for wider publication. But she has never told us much, even after the story of Enigma was published in the 1980s.

She had been recruited because her parents lived near Bletchley and she spoke fluent French and good German. One brother was a fighter pilot who survived the Battle of Britain and, miraculously, the whole war too; the other was an army doctor who went over with the first wave of troops on D-day – he didn't talk much about his experiences either.

She was a proper cryptanalyst, working for John Tiltman, one of the giants of the field. It is a shock to discover one of the Americans with whom she exchanged Christmas cards until he died is listed in the NSA's official tribute to Tiltman – William Filby, not to be confused with Kim Philby, whom she met a few times, although as a young man listening to her stories I was tempted to confuse them.

In the years since the story was first revealed a mythology has grown around it – an authorised version of the story; it's obviously factually true, but it has almost nothing to do with the way she remembers her time there. My father used to say that she had cracked a vital part of a German naval cypher, but all she will say now is that she found a repeat in something and everyone got excited.

"Colonel Tiltman gave me various knotty problems to work on," she says. "I and a Russian émigré named Fetterlein used to work together. 'Oh, Patreesha, zis is awful,' he would say, and that was our catchphrase."

So I googled Fetterlein and discovered from the NSA's official history that he had been recalled from retirement to work at Bletchley, having been the chief cryptographic officer of the tsar's government, "holding the ranks of both admiral and general. Following the Bolshevik revolution he walked across the Finnish border and made his way to Great Britain."

There he helped train Tiltman himself. It is an extraordinary thought that my mother worked with the Tsar's chief cryptanalyst. But she has never subscribed to the myth that Bletchley was the heart of the war effort. In part this is because she never worked on Enigma herself. She knew Enigma codebreaker Alan Turing, but he made no great impression on her. Partly it is because the ethos of the place and time was opposed to boastfulness. There is, I think, a more important reason: Bletchley was never bombed and no one there was in imminent danger of death. They worked enormously hard – my mother was off work for a year with a breakdown – but they thought, and I believe the survivors still think, that they were only doing their duty. When you're actually fighting a war the quality that is really admirable is courage, and both she and her fighter pilot brother would have laughed at the idea that she did more to ensure victory in her cold cramped hut than he did in the cockpit of his Spitfire.

Every generation picks its heroes, and there is always a touch of wish fulfilment about the ones they choose. When I was a boy, I wanted to be a fighter pilot more than anything else and I almost fainted with reverence at Uncle Tony's second wedding when he introduced me to Brian Kingcombe. That he had been married to a famous actress before then made no impression on me at all. Paying our respects instead to the people who fought with their brains may be a moral advance, but I think it's just a shift sideways. Turing was a genius and the victim of a horrible injustice. But the war was won as much by the endurance and courage of everyone who was not a genius, and it's a great deal harder to emulate that than to imagine ourselves making breakthroughs of astonishing brilliance or dazzling at the controls of a Spitfire.