Frederick Lindemann, Viscount Cherwell, was one of the most influential yet least known figures of the 20th century. Born in 1886, he became Winston Churchill's scientific adviser and close friend and reached the pinnacle of political, scientific and social life in Britain. During the 1930s, Lindemann campaigned strenuously against appeasement and moved to the centre of policy-making when he joined the Cabinet. He advised on all the central issues of the war, including the U-boat threat, the bombing of Germany, the V-weapon peril and the creation of the atom bomb. A gifted musician and sportsman, as a young man he played tennis against both the Kaiser and the Czar. He went on to become one of the world's leading figures in science's heroic age. He championed and befriended Einstein. He repeatedly risked his own life - and saved many others - in demonstrating how to escape from aeroplane spin. And, between the wars, he established almost from scratch Oxford University's international reputation in physics.