Thornton was a familiar face on British television, especially in comedies. He is best known for playing Captain Stephen Peacock in the long-running sitcom, Are You Being Served. Thornton starred as Peacock, a snooty floorwalker with a dubious military record, from 1972-85, and again in the early Nineties in spin-off show Grace and Favour. He was one of the last of the surviving cast from the sitcom, with Nicholas Smith, who played department manager Mr Rumbold.