He was a male lead in Italian genre films, most notably Mario Bava's Black Sunday (1960) with Barbara Steele, but he was best known for playing the love interest of Ursula Andress in She (1965) and then of Raquel Welch in One Million Years B.C.

His first role of note was in the Italian gothic horror film, Black Sunday (1960), directed by Mario Bava, which starred fellow British actress Barbara Steele.

[3] Richardson's big breakthrough came when Ray Stark spotted him in the offices of Seven Arts Productions and cast him as the male lead in She (1965), which they were co-producing with Hammer Films.

In the late 1960s, he was considered for the role of James Bond in On Her Majesty's Secret Service (1969) when Sean Connery first left the franchise, but he lost out to George Lazenby.

[6][7][8] That year, Richardson based himself out of Italy once more and appeared in some giallo films: Torso (1973), Eyeball (1975), Reflections in Black (1975), Nine Guests for a Crime (1977), and Murder Obsession (1981).