[1][2][3] Born in Lisbon, Portugal, and brought up in Scotland, he had a long and successful career in film and television, appearing in a variety of high-profile productions.

On film, he appeared in The Man in the White Suit (1951, as Harry), The Adventures of Quentin Durward (1955, as the villain De La Marck), The 39 Steps (1959, as Kennedy), Ben-Hur (1959, as Marius, an associate of Messala), Mutiny on the Bounty (1962, as John Williams), Arabesque (1966, as Kyle Webster) and Battle of Britain (1969, as Flight Sergeant Arthur).

From 1958 to 1960, Lamont was a semi-regular as David MacMorris in the CBS western television series, The Texan, starring Rory Calhoun.

[5] Lamont also appeared in guest roles in a range of popular British programmes from the 1950s to the 1970s, including The Adventures of Robin Hood, Dixon of Dock Green, Danger Man, The Avengers, Callan, Secret Army, Randall and Hopkirk (Deceased), The Persuaders!

In 1953, he appeared in the major role of astronaut Victor Carroon in Nigel Kneale's ground-breaking BBC science-fiction serial The Quatermass Experiment, and fourteen years later returned to the series when he played the role of Sladden in the Hammer Films version of the third serial, Quatermass and the Pit.