Holt was born during the first quarter of 1930 in Uxbridge, Middlesex, and met Derek Meddings while at school. He started working in a laboratory at Denham Film Studios in 1944, and stayed with the studios for seven years. In 1951, Holt went for an interview at MGM when he saw that the company required somebody who knew sensitometry. Following an interview, he got the job, which involved doing the opticals, miniature photography, special effects, and back projection.