They were all spy-conscious in Washington now, but such anecdotes apart, the central event of Alan's visit was the breakthrough back into the U-boat Enigma.
This was achieved without the possession of faster Bombes; it depended upon a precarious thread of luck, ingenuity, and a German blunder.
It went back to the weather signals that in mid-1941 had given them an almost unfairly simple crib each day, thanks to the fact that they were transmitted both in the Enigma, and in the special meteorological cipher.
But early in 1942 a change in the system had denied this method to Hut 8. Not until the U-boat capture of 30 October could it be regained.
This gave them the cribs, but the difficulty remained that it would take three weeks to work through all the rotor settings, just for one day's traffic.
Here, however, they were saved by a German blunder which, in effect, threw away all the advantage that the fourth wheel offered.
For the weather reports, and other routine short signals, the U-boats used their Enigma with the fourth wheel in 'neutral' position, thus reducing the cryptanalysts' problem to the one they had mastered in 1941.
This in itself was not fatal for Germany; the greater mistake lay in the fact that the three rotor settings used for the weather reports were also used for all the other traffic of the day.
For this the analysts now needed only to work through 26 possibilities for the fourth wheel, rather than the 26 × 336 × 17576 possibilities that would otherwise have been the case.
As a result of this slip, Hut 8 was able to supply decrypted messages from 13 December.
They had weeks in which nothing worked out.
But it was sufficiently copious a flow of information for the Tracking Room in the OIC to have by 21 December a clear idea of the location of all eighty-four U-boats at large in the North Atlantic.
And this time Hut 8 was not alone. In Washington, Alan Turing was indoctrinating the American analysts into all their methods.
Now, when the rotor settings were discovered, they were passed back and forth across the Atlantic, the analysts beginning to communicate directly as indeed the two tracking rooms were also doing.