Books: Invisible Army C

In the official records he had no title, position or office: he did not exist. But in fact Winston Churchill's spymaster, Sir Stewart Graham Menzies, deserves as much credit for the Allied victory in World War II as most of the generals who won the battles. His amassed information formed the invisible army that marched into Germany with Eisenhower, Montgomery and Patton. It is past time for this engrossing if overlong biography of the war's most mysterious player.

Born in 1890, Menzies was one of the golden boys of the British aristocracy. His family was rich and well placed, and he...