Archibald Sinclair, a wealthy landowner from the north of Scotland, was Liberal Party leader from 1935 to 1945 and Air Minister throughout Winston Churchill's ministry during World War II. A widely-admired and talented politician, he played an important part in the major controversies of mid-century: appeasement, unemployment policy, the Abdication, rearmament and the war. His integrity, civility and sense of humour set him apart in an age of opportunism and betrayal. A devout believer in Liberalism, Sinclair carried his party through its dark age. Under his leadership, the demoralized and disintegrated 19th-century relic was finally modernized. That a party - or a version of it - survives to this day is largely due to Sinclair. As Air Minister he played a crucially important role in both the Battle of Britain and the strategic bombing of Germany. He locked horns with Churchill, Beaverbrook, Hugh Dowding and Bomber Harris. Many wished to destroy him. His survival in office from 1940 till 1945 is testimony to his remarkable skill and resilience. Sinclair was a lifelong friend and confidant of Churchill. This biography includes much previously unpublished correspondence between the two men and provides revealing glimpses of many other important figures of the day.