Winston Churchill enjoyed two stints as First Lord of the Admiralty, at the start of the First World War and at the start of the Second. He retained close interest in naval matters, especially as the defeat of the U-boat menace was so vital in both wars to maintain the vital supplies so necessary for Britain's war efforts. Indeed, Churchill later said that this was the only thing that had threatened the ultimate Allied victory. AUTHOR: Captain Stephen Roskill was born in 1903 and educated at the Royal Naval Colleges of Osborne and Dartmouth. He commanded HMS Warspite at the beginning of the Second World War before being attached to the Naval Staff. After further sea service, he became Deputy Director of Naval Intelligence. He wrote the Official History of the Royal Navy in World War Two in four volumes, and knew Churchill and most of the Royal Navy officers about which he writes. 12 b/w illustrations