William Willcocks was born 150 years ago in a tent beside a canal in northern India, where his father worked for the colonial government. He learnt his engineering in India before heading for Egypt in 1883. There he rose to become director-general of reservoirs, and a legend on the banks of the Nile. He built the first Aswan dam, then the largest in the world, went on to revive the ancient irrigation systems of Mesopotamia, and watered deserts from south Africa to India. But he was deeply troubled by the discovery that much of what his fellow water engineers did in their colonial playgrounds was worse than useless.