Even with Germany in the ascendency at the beginning of World War II, Scapa Flow was supposed to be the safe home base of the British Navy. Nothing and nobody could penetrate the defences of this bastion, which was built up to formidable levels in World War I and symbolized the faith placed by the British in the invulnerability of their navy. So how, in the dead of night on October 13, was Gunther Prien's U-47 able to slip through the line of protective warships undetected to sink the mighty Royal Oak? This book provides the answer with an account of one of the most daring naval raids of World War II indeed - in all of history. Drawing on the very latest underwater archaeological research, this study explains how Prien and his crew navigated the North Sea, Kirk Sound and some very unlikely odds to land a devastating blow on the British, and became among the very first German heroes of World War II. It reveals the level of disrepair that Scapa Flow had fallen into, and delves into the intriguing conspiracy theories surrounding the event, including an alleged cover-up by the then First Sea Lord, Winston Churchill.