William Lees was born in Largs, Ayrshire, on 21 April 1923. He was the son of Craig Lees, a tailor, and Agnes Mary Storm née Love, the daughter of a stockbroker. He was educated at Ardrossan Academy and Glasgow University, and he completed junior posts at the Royal Infirmary, Glasgow, where he was much influenced by Arthur Jacobs. He did his National Service in the RNVR, completing his surgical training at Glasgow Royal Infirmary and Swansea Hospital. He was appointed consultant surgeon to Bishop Auckland and Dryburn Hospital, Durham. In 1967, he married Elizabeth Carol Owen. They had two sons and a daughter. He died in February 2002.