The men and women of Bletchley Park, who repeatedly broke German military cyphers throughout the Second World War, made an incalculable contribution to the allied success. This book, written by one of the code-breakers provides a fascinating insight into the process.

Despite the core subject, this is not really a book about cryptography, but about how to manage people and technology to solve complex, important problems. Welchman was the "glue" between the pure ideas men like Alan Turing, and the code-breaking production line. His talents were clearly in building the organization, and liaising between the different parties so that interception, decoding, understanding and using the intelligence became a repeatable success.

Welchman's insights into British wartime society and bureaucracy are keen and frequently very humourous. Many of his insights are equally applicable today, in business as well as military circles.

Although he was very modest about it, it is clear that Welchman was no mean cryptologist himself. The book does attempt to explain several of the ways in which Enigma was cracked, but I found the primarily verbal explanations difficult to follow. However, this doesn't prevent an understanding of the principles, and how different methods were applied at different points during the war.