The story of the Black Hole of Calcutta was once drilled into every British schoolchild: how in 1756 the Nawab of Bengal attacked Fort William and locked the survivors in a tiny cell, where over a hundred souls died in insufferable heat. British retribution was swift and merciless, and led to much of India falling completely under colonial dominion. The Black Hole is the story of the propagation of a myth that arose as the British Empire came into being: a myth about the barbarism of a people the colonials sought to rule, and how that myth - based on improbable exaggeration and half-truth - helped justify the march of empire for two hundred years.