Ordered a paperback from Amazon a month or so ago called "Very Special Intelligence" by Patrick Beesly.
I am finally just starting into this book. Its dry but very interesting, more fact over prose.
Operational Intelligence Centre was the nerve centre of British naval operations during World War II. Patrick Beesly served there from 1940 to 1945 and describes how intelligence was gathered and how it was used to defeat Hitler and his admirals.