What Vladimir Putin has called the greatest disaster of the 20th century most of the Western world call its greatest success: over six months the Soviet Union imploded, causing as little collateral damage as a professionally demolished tower block. Whatever we have to worry about now in the world is no threat to our sleep, unlike during the forty years before 1991, when one did not have to be paranoid to fear global annihilation in a Soviet–NATO nuclear war. Whether the USSR is truly the last empire to collapse might, however, be disputed: China, no matter how large its Han majority, still has colonial subjects – Uighurs, Mongols and Tibetans – dreaming of independence.

The USSR’s end was unique: the country had not, like the collapsing empires of 1918, been irreparably damaged by war; nor, as the British, French and Portuguese were in the decades after the Second World War, was it faced with simultaneous rebellions in colonies thousands of miles away. The ruinous