The book, "Blind Mans Buff" about US (and some UK) submarine int gathering ops is also a very good read.
Puts me in mind of a tale in the early post-perestroika days:
At some cockers P or other, mates are in conversation with some ex-Sov. Mil type. During the conversation, mate discloses that he lived in South Devon. "Ah - a very pretty part of England", remarked the Sov. Mate then askes how he knew that, given that there were big restrictions on where he could travel when in the UK.
"Was not a problem. You see, I was on submarines" came the reply....