A Lexicon of Cryptography (“Most Secret”, Bletchley Park, 1943) LATER, IT WOULD transpire that Bletchley Park knew almost everything there was to know about U-653. They knew she was a Type VIIc—220 feet long, 20 feet wide, with a submerged displacement of 871 tons and a surface range of 6,500 miles—and that she had been manufactured by the Howaldts Werke of Hamburg, with engines by Blohm und Voss. They knew she was eighteen months old, because they had broken the signals describing her sea-trials in the autumn of 1941. They knew she was under the command of Kapitanleutnant Gerhard Feiler. And they knew that on the night of 28 January 1943—the final night, as it happened, that Tom Jericho had spent with Claire Romilly—U-653 had slipped her moorings at the French naval port of Saint-Nazaire and had moved out under a dark and moonless sky into the Bay of Biscay to begin her sixth operational tour. After she had been at sea for a week, the cryptanalysts in Hut 8 broke a signal from U-boat headquarters—then still in their grand apartment building off the Bois de Boulogne in Paris—ordering U-653 to proceed on the surface to naval grid square KD 63 “AT MAXIMUM MAINTAINABLE SPEED WITHOUT REGARD TO THE THREAT FROM THE AIR”.
