In 1860, an eccentric Irish police officer named Robert O’Hara Burke led a cavalcade of camels, wagons and men out of Melbourne. Accompanied by William Wills, a shy English scientist, he was prepared to risk everything to become the first European to cross the Australian continent. A few months later, an ancient coolibah tree at Cooper Creek bore a strange carving: ‘Dig Under 3ft NW’. Burke, Wills and five other men were dead. The expedition had become an astonishing tragedy.