The real game was the Lorenz-stye encryptors that were used for communications between German commands. These delivered the strategic information about mid-to longterm movement of units and so on which allowed they Allies to correctly anticipate attacks. These were the messages that Colossus was used to decrypt, as opposed to the Bombes which were decrypting Enigma traffic, and which were largely derivative of earlier Polish efforts to decrypt Enigma.
I read a book a while back https://www.goodreads.com/book/show/1127838.Colossus that looks at all of this in detail. Surprisingly, if the book is correct, Turing seemed to have limited contact with the Colossus effort, and was more involved with the Enigma decryption. The Colossus people didn't seem to be terribly occupied by ideas such as Turing-completeness, they were just building machines that were capable of doing certain operations at high speed.