Enigma Machine and Its U-boat Codes

Believing their ship sank, none of U-110's survivors (there were ultimately thirty-two - see Aubrietia’s 9 May Report of Attack, at 1430 GMT) knew about Balme's boarding party. (They were quickly brought below deck on the rescue ship.) Four hundred men from the British Royal Navy knew about “Operation Primrose” (as the capture was thereafter called), but not one said a word about U-110's treasure until after the war was over.

Initially towing U-110 back to Iceland, the Royal Navy crews knew their find would be useless if Germany learned U-110 had been captured, not sunk. Had they learned the truth, the Germans would have changed their system immediately and British code breakers would have been unable to make good use of the sealed June codes David Balme had found.

At 11 a.m. the next morning, after the wind “had increased to force 6 with a nasty lumpy sea," U-110 suddenly “began to sink by the stern.” Soon thereafter, “her bow was standing vertically out of the water.” (See paragraphs 13 and 14 of Commander Baker-Creswell’s “Most Secret” report dated 10th May, 1941.) She could not survive the 400-mile tow to Iceland and disappeared into the sea. The Enigma machine and all supporting data were turned over to Alan Turing and his team at Bletchley Park, near London.