Enigma

London to Scotland split it down the middle, and then the smaller branch line from Oxford to Cambridge sliced it into quarters, so that wherever you stood there was no escaping the trains: the noise of them, the smell of their soot, the sight of their brown smoke rising above the clustered roofs. Even the terraced houses were mostly railway-built, cut from the same red brick as the station and the engine sheds, constructed in the same dour, industrial style.
    The Commercial Guesthouse, Albion Street, was about five minutes' walk from Bletchley Park and backed on to the main line. Its owner, Mrs Ethel Armstrong, was, like her establishment, a little over fifty years old, solidly built, with a forbidding, late-Victorian aspect. Her husband had died of a heart attack a month after the outbreak of war, whereupon she had converted their four-storey property into a small hotel. Like the other townspeople—and there were about seven thousand of them—she had no idea of what went on in the grounds of the mansion up the road, and even less interest. It was profitable, that was all that mattered to her. She charged thirty-eight shillings a week and expected her five residents, in return for meals, to hand over all their food-rationing coupons. As a result, by the spring of 1943, She thousand pounds in War Savings Bonds and enough edible goods hoarded in her cellar to open a medium-sized grocery store.
    It was on the Wednesday that one of her rooms had become vacant, and on the Friday that she had been served a billeting notice requiring her to provide accommodation to a Mr Thomas Jericho. His possessions from his previous address had been delivered to her door that same morning: two boxes of personal effects and an ancient iron bicycle. The bicycle she wheeled into the back yard. The boxes she carried upstairs.
    One carton was full of books. A couple of Agatha Christies. A Synopsis of Elementary Results in Pure and Applied Mathematics, two volumes, by a fellow named George Shoobridge Garr. Principia Mathematical, whatever that was. A pamphlet with a suspiciously Germanic ring to it—On Computable Numbers, with an Application to the Entscheidungs problem—inscribed 'To Tom, with fond respect, Alan'. More books full of mathematics, one so repeatedly read it was almost falling to pieces and stuffed full of markers—bus and tram tickets, a beer mat, even a blade of grass. It fell open at a heavily underlined passage:
    there is one purpose at any rate which the real mathematics may serve in war. When the world is mad, a mathematician may find in mathematics an incomparable anodyne. For mathematics is, of all the arts and sciences, the most remote.
    Well, the last line's true enough, she thought. She closed the book, turned it around and squinted at the spine: A Mathematician's Apology by G. H. Hardy, Cambridge University Press.
    The other box also yielded little of interest. A Victorian etching of King's College Chapel. A cheap Waralarm clock, set to go off at eleven, in a black fibre case. A wireless. An academic mortarboard and a dusty gown. A bottle of ink. A telescope. A copy of The Times dated 23 December 1942, folded to the crossword, which had been filled in by two different hands, one very small and precise, the other rounder, probably feminine. Written above it was 2712815. And, finally, at the bottom of the carton, a map, which, when she unfolded it, proved not to be of England, or even (as she had suspected and secretly hoped) of Germany, but of the night sky.
    She was so put off by this dreary collection that when, at half past midnight that night, there was a knock on the door and another two suitcases were delivered by a small man with a northern accent, she didn't even bother to open them but dumped them straight in the empty room.
    Their owner arrived at nine o'clock on Saturday morning. She was sure of the time, she explained later to her next-door neighbour, Mrs Scratchwood, because the religious service was just ending on the wireless and the news was about to start. And he was exactly as she'd suspected he would be. He wasn't very tall. He was thin. Bookish. Ill-looking, and nursing his arm, as if he'd just injured it. He hadn't shaved, was as white as—well, she was going to say 'as a sheet', but she hadn't seen sheets that white since before the war, certainly not in her house. His clothes were of good quality, but in a mess: she noticed there was a button missing on his overcoat. He was pleasant enough,