Timing is all but even Hugh Sebag-Montefiore could hardly have dreamed when he started researching this book four years ago that its publication would coincide with the release of the Hollywood blockbuster U-571. The film claims that it was the Americans "wot won the war" through the bravery of two of its sailors who climbed aboard the crippled sub and made off with an Enigma machine and assorted codebooks before it sank. But then Hollywood has never let the facts get in the way of a good profit. As Sebag-Montefiore points out it was a British officer, Francis Fasson, together with Able Seaman, Colin Grazier, who climbed down the turret of U-559 to retrieve the codebooks and, furthermore, their capture was only a small, if important, part of the Enigma story. However, this book is neither an exercise in point scoring nor full of dramatic new revelations. Its purpose is to chart the entire Enigma history from 1931, when a cipher officer, named Hans Thilo Schmidt, working in the German Defence Ministry, first passed secrets of the code to the French to the end of the War. As such it is extremely welcome. There have been a fair number of books on various parts of the Enigma story--not least the work of Alan Turing and the Bletchley Park boffins--but there have been few that have so thoroughly charted the early years of the 1930s when Polish cryptographers battled to read Enigma messages. Thus Enigma becomes part of an ongoing story, not something just bolted on to a dramatic narrative of the Second World War. Sebag-Montefiore has unearthed a few new primary sources, who add colour and insight rather than anything new, but he does have an engagingly easy style not found among many historians and the book is an extremely accessible read. For all its thoroughness, though, there are some things that the author cannot explain. Why did the Germans not realise the code was broken when all the evidence pointed that way? And how did Enigma work? Sebag-Montefiore devotes a lengthy appendix to a simplified explanation of the latter--but this reader is still none the wiser. Maybe some things will always remain a mystery. --John Crace