The extraordinary tale of the father of modern geology. Hidden behind velvet curtains above a stairway in a house in London's Piccadilly is an enormous and beautiful hand-coloured map - the first geological map of anywhere in the world. Its maker was a farmer's son named William Smith. Born in 1769 his life was beset by troubles: he was imprisoned for debt, turned out of his home, his work was plagiarised, his wife went insane and the scientific establishment shunned him. It was not until 1829, when a Yorkshire aristocrat recognised his genius, that he was returned to London in triumph: The Map That Changed the World is his story.