Having waited so long to hear more of the latest 'secrets' from Bletchley Park one might ask what else could possibly not have already been put into print. This book concentrates on Colossus, exposing a 30 year old smoke screen using the Enigma story to deflect attention away from another of their successes, protecting modern secrets of GCHQ. The book is well-written, contains references to supporting texts and tells a story which will be hard to follow. The book contains an accurate technical picture of the colossal achievments, perhaps close to the limits necesssary to still make the 60 year old machine a national secret.