Two of the ancient cities now being destroyed by Islamic State lay buried for 2,500 years, it was only 170 years ago that they began to be dug up and stripped of their treasures. The excavations arguably paved the way for IS to smash what remained - but also ensured that some of the riches of a lost civilisation were saved. In 1872, in a backroom of the British Museum, a man called George Smith spent the darkening days of November bent over a broken clay tablet. It was one of thousands of fragments from recent excavations in northern Iraq,...