So Alan Turing re-entered the ruined land of Gauss and Hilbert under watchful American eyes and in a military jeep.
The party stayed at a communications laboratory at Ebermannstadt, near Bayreuth, which they had to reach by trudging up a thousand feet of mountain.
It had been a hospital, and still bore a red cross on its roof, so they simply slept in the hospital beds.
Women from the village came and did their washing, in return for a fragment of soap.
Only he and Flowers had any cryptological interest, and the other members of the party did not (as far as they knew) know that they had.
One of the captured German scientists proudly produced a machine of the Fish type, and explained how many billions of steps it would go through without repeating the key.
Alan and Flowers just blinked and said, 'Really!' when he went on to tell them that none the less their mathematicians had reckoned it impregnable only for two years, and that then there would be a chance of it being broken.
While they were there, the mushroom cloud fulfilled the wilder prophecies of 1939.
The quantum mechanics that Hardy had so recently pronounced gloriously useless, had come of age. It was the outward sign of the new men's work.
Maurice Pryce had played an early part in the British research, and the final touch had been added by von Neumann, calculating the height at which it should explode to effect the maximum destruction.
The clouds rolled over the second enemy, that would-be latecomer to old-fashioned empire, and warned a potential new one.
The Americans had solved the final problem of the war.
Yet without the sequence of events that had kept the Enigma on the Allied side in 1943, the war of 1945 might have been very different, with the first atomic weapons reserved for the concrete pens of raiding U-boats.