Sir, The cancellation of Operation Ruthless in October 1940 (report, April 7), was met with dismay in Bletchley Park. Much store had been set by this opportunity to assist in the recovery of the daily key of the German naval Enigma, which was proving extremely difficult to resolve.

Frank Birch, head of the naval section in Bletchley Park, had described Ruthless as a “very ingenious plot”: it gave away nothing if it failed. On October 20 he wrote to a colleague: “\ Turing and \ Twinn came to me like undertakers cheated of a nice corpse two days ago, all in a stew about the cancellation of Operation Ruthless. The burden of their song was the importance of a pinch. Did the authorities realise that, since the Germans did the dirt on their machine on June 1 (ie, changed the method of assembling the key), there was very little hope, if any, of their deciphering current, or even approximately current, enigma for months and months and months — if ever? Contrariwise, if they got a pinch, even enough to give a clue to deciphering one day’s material, they could be pretty sure, after an initial delay, of keeping going from day to day from then on . . . ”

Ian Fleming told Birch that the value of a pinch was well recognised and that Ruthless had only been postponed. It was never to be revived. Not to be denied, in May and June 1941, at the instigation of Harry Hinsley, another member of the naval section in Bletchley Park, two German weather ships off Iceland were deliberately targeted and captured by the Royal Navy. The cipher material obtained was to be of immense importance in breaking the German naval Enigma daily key settings.

Full details of Operation Ruthless can be found in the National Archive.

Peter Wescombe

Bletchley Park Trust

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