William  qualified as a lawyer at Cambridge, practising at Middle Temple in London before returning in 1939 to the Johannesburg Bar. Called up to fight in World War ll, he served as an artilleryman and air intelligence liaison officer. By the time the war ended in 1945 he was, at the age of 30, one of the youngest lieutenant-colonels in the army, highly regarded as an effective leader. In 1946, he left the Bar to join Anglo American at a time of unprecedented growth and went on to become Managing Director in 1957.