Alfred Hawthorne Hill was born in Southampton and attended Taunton's School. During World War II, he was evacuated to Bournemouth.
After leaving school, Hill worked at Woolworth's, as a milkman, a bridge operator, a driver and a drummer before he finally got a foot in the door of the entertainment industry by becoming assistant stage manager with a touring review. He was called up in 1942 and trained as a mechanic, but transferred to the Combined Services Entertainment division before the end of the war. It was there that he met his future agent, Richard Stone, then a colonel.
Inspired by the "star comedians" of British music hall shows, Hill set out to make his mark in show business. For the stage, he changed his first name to 'Benny', in homage to his favourite comedian, Jack Benny. Hill began appearing at working men's clubs and dinners before moving on to nightclub and theatre jobs. Hill auditioned for Soho's famed Windmill Theatre (home of Revudeville, a popular show of singers, comedians and nude girls), but he was not hired. Hill's first job in professional theatre as a performer was as Reg Varney's straight man, beating a then unknown Peter Sellers to the role.