Did Alan Turing's decryption team develop an statistical analysis algorithm to decide whether to use information from decrypted Enigma messages without risking the Germans to find out that they had broken the code, as depicted in the film The Imitation Game?
I would have thought those decisions were made at a much higher level. Some sources claim that the scene in the movie where they decide not to save the brother of one of the members of the team so that the Germans don't suspect that the code has been broken, is fiction. However, there is a scene later where Turing suggests to Menzies (the head of British secret intelligence) that they could develop a method based on statistical analysis to decide when to use the code, only so that they could win the war, but not too much so that the Germans never find out that the code has been broken. The actual meeting between Turing and Menzies probably did not occur, since Turing did not meet him. But the question remains whether Turing (or any of the codebreakers) ever helped to develop or suggested to develop such a statistical analysis.
Other sources claim that in fact, it was Menzies who came up with Ultra, which was the name given to the system to determine which messages to use. Did Alan Turing, or any of the mathematicians in his team, have anything to do with Ultra? Exactly who were the people (besides Menzies) involved in the development of Ultra?