Much more about the general exploits of HMS Petard which therefore includes a brief mention of the capture of the papers needed to break into Germany's naval Enigma codes. Vast, unacknowledged bravery (at the time, due to security) for sure.
I got a little irritated at the bulk of the book which chronicled various other wartime missions with nothing at all to do with Enigma. Interesting in its own right - though occasionally reading a little like a list of diary entries: "went here, did that; dry-docked; went there, did this; ..." - it was not what I expected from a book with this title.