A small tablet was found in modern Iraq and brought back to the British Museum. When it was translated, back in 1872, it turned out to be an account of a great flood that significantly pre-dated the famous Biblical tale of Noah. This discovery caused a storm around the world and led to a passionate debate about the truth of the Bible - about story telling and the universality of legend. In a week that looks at the emergence new ways of expression like literature and mathematics, Neil MacGregor introduces us first to the British Museum's provocative "Flood Tablet".