A DRAUGHTY wooden hut, in the company of the best brains of Britain, was not quite the billet Jane Fawcett had imagined for herself. At Miss Ironside’s School for Girls in Kensington the drill had been to sit up straight, learn to curtsey and not bother her head about exams, for Mr Right was bound to come along eventually. After that, in 1939, she was a deb, parading en masse in a long white frock and an obvious sulk. A complete waste of time, she thought. Now, aged 19, just a chicken in the Bletchley Park code-breaking team, she was spending hours on a horrid hard chair, bent over a machine on a wobbly trestletable. Lights hung down on strings, and a frightful old stove smoked in the middle of the room. She was also saving the country, and it was terribly exciting. But she could not breathe a word about that.

She had told her parents she was working for the Foreign Office. They probably presumed it was as a typist, the kiss of death. She had been recruited for Bletchley because the government then believed that the upper classes were better at keeping secrets. Such an odd idea; she’d supposed the whole country was making common cause. She often didn’t think much of aristocrats, despite moving in that world herself.

It was certainly a relief, though, when her father rescued her from her first lodgings, in a fume-ridden council house with a lorry-driver’s family. Couldn’t have Jane there, he said. She moved to Liscombe Park, the Elizabethan mansion of a family friend, where a much jollier time was had, though the trip to Bletchley down pitch-black country lanes for night shifts was hairy, to say the least. Bletchley Park itself, a pile of best “lavatory Gothic” as she later described it, was sociable for a spy-centre; she danced Scottish reels on the lawn and sang madrigals. Those gave brief respite from the gruelling days and nights spent tracking what the Germans were up to.

Her enemy was the German Enigma machine, a fiendish configuration of rotors which changed every day to set the code for Nazi military communications. Bletchley Park’s code-breaker, known as the Bombe, was being ever-upgraded to compete with it by a group of laconic, obsessive men (including Alan Turing, “desperately screwed up”, and Gordon Welchman, “always in the depths of the deepest thought”). Of course, they never noticed her. Yet women, two-thirds of the workforce, were treated pretty much as equals at Bletchley. They could notch up their own victories, and May 25th 1941 was hers.

The day was going as usual. When an Enigma code was broken, she would check the decoded message to see, one, if it was plausible German, and two, if it was of any interest. (She had all of six months of German, picked up in dull Zurich, where she had been sent to get over her heartbreak that she was too tall to be a ballerina. She soon went off to St Moritz instead.) In May 1941 they were all trying to trace the Germans’ best battleship, the Bismarck, which had just destroyed HMS Hood with the loss of more than 1,400 lives. They thought it was still off Norway. But the decoded message, spooling on a paper strip out of her machine, told her that the Bismarck was going to Brest. The message was passed straight to Whitehall, and they were all “absolutely on their toes” to know what would come through next. It was a distress call, as Hitler’s finest ship was sunk by the Royal Navy. That earned her a rousing cheer in the Bletchley Park dining room.

A red-brick victory

And that was all she got. No one outside the circle knew anything of it; they were all sworn to absolute secrecy for life. That was sometimes very hard. Her fiancé Ted, a naval officer, came back from the war a hero; she felt like an also-ran. Nonetheless, not being one to brood, she became a professional singer for 15 years while bringing up two children; and then, unexpectedly, got the chance to charge off to war again. Which, of course, she did.

This time the secret central command was in her own house in Kensington. There, as secretary from 1964 to 1976, she ran the affairs of the Victorian Society. Once more, it was David against Goliath: a small group led by another obsessive intellectual, Nikolaus Pevsner, fighting tooth and nail to persuade the whole government, the whole of the British public, all academe and almost all architects that Britain’s Victorian buildings were worth saving. Once more, too, it was she who did most of the hard slog. She wrote books, lectured, managed the rickety finances and tormented British Rail while the men, especially John Betjeman, the poet, grabbed the attention. Well, never mind; she counted saving the rampant red-brick London Midland Hotel beside St Pancras as one of her special achievements. And she was even happier to see how good it looked inside when it reopened in 2011. She had feared the redo would be very vulgar.

The refurbishment that pleased her less was of Hut 6 at Bletchley. At last, the great secret got out; the place became a museum, and she went to see it. The lawns were too neat, the lights were wrong and the tables no longer wobbled. It was all much too clean and rather sterile. Still, that didn’t stop her seizing the hand of the Duchess of Cambridge and chatting away briskly for ages, as one well-bred gel to another, about the best time of her life, spent there.