Another book with some insight into Bletchley Park is "Cloak and Gown" (I forget the author), about the relationship between Yale academics and the OSS, the WW2 predecessor to the CIA. Among the various Yalies who went into the OSS was James Jesus Angleton, who spent a lot of time at Bletchley analyzing information that might be useful for US Army and covert OSS activities, and trying to support counterintelligene work by correlating the information from intercepts of German understanding of US and British plans with the Allied sources and users of those plans, to try to find leaks, traitors, moles, spies, and other types that counter-spook spooks worry about. Besides the Enigma interceptions themselves, the big secret the OSS and British intelligence were paranoid about protecting was that all the known German spies in Great Britain had been caught and turned for disinformation use (or killed); almost everything Germany was getting from its spies was bogus. Bill