For those interested in Bletchley Park, it features prominently in the book Between Silk and Cyanide: A Codemaker's War by Leo Marks. I read it maybe 10 years

For those interested in Bletchley Park, it features prominently in the book Between Silk and Cyanide: A Codemaker's War by Leo Marks. I read it maybe 10 years ago and it has a lot of good stuff about WWII codes and spying.