To release the cat here ~ From somewhere in my mind I have come across some plausible info cannot state when/where many years ago but as we know the allies did eventually get hold of a 4 rotor Enigma they sent convoys out full well knowing the disposition of the enemy they did not send all of them towards the U-Boats but enough to deceive the Germans that their Kreigsmarine Enigma was not compromised. As had all of a sudden things gone quiet for the U-Boats then the games up and they may have designed a 5th rotor'ed one.
Now if this in fact did happen can you imagine the furor of relatives who found out that lives were sacrificed, I am in agreeance that some operational stuff should remain classified as things had to be done to overcome a tyranny that threatened our whole way of life on this rock.