In the mid-19th century, around lunchtime, a pale young man with an enormous beard could be seen in the British Museum reading room poring over piles of books about Mesopotamia. His name was George Smith, and this was his secret passion. Then, one day, a museum attendant remarked that it was a shame no one had bothered to decipher ‘them bird tracks’ — by which he meant the weird-looking scratches in clay tablets from the newly rediscovered ancient city of Nineveh.