A biography of the little known, prolific and rather strange mathematical genius who for six decades thought and wrote maths for nineteen hours a day, seven days a week, until his death aged 83. Fuelled by espresso and amphetamines he toured the world with his mother in tow, racing across continents to mathematicians' doorsteps with the object of proving as many theorems as possible. A vivid and moving portrait of a man who had no home, wife or other interests and never learnt to cook or do the laundry. "A marvellous biography that brings out not only his genius, but his warmth and sense of fun" Oliver Sacks.