This is a biography of Dillwyn Knox - Dilly - one of the key British cryptanalysts, who served as a member of Room 40 in WWI, in GC&CS between the wars and a founder member of of Bletchley Park. It was recently published in paperback.
Knox was eccentric and somewhat difficult. the author, Mavis Batey, worked for him during the war. She has been able to apply her own knowledge to inform her portrait, without letting her affection interfere with her analysis..
I really enjoyed this book, and regard it as an excellent account. Do others agree