Finch was born in Caterham, Surrey, the son of a merchant banker. He first started acting at school, later gaining experience in amateur theatre groups. After serving in a parachute regiment during his military service, he joined an SAS reserve regiment.　　Finch had started acting professionally with several different repertory companies around the UK before he got a part in Crossroads, the popular daytime soap, during its first run in 1964. Finch then appeared in Z-Cars (1967-68) and in 10 episodes of Counterstrike (1969), a short-lived BBC sci-fi series about an alien (Finch) sent to Earth to save it from extinction.　　His film career began in two hammy Hammer horrors, The Vampire Lovers and The Horror of Frankenstein (both 1970). Polanski, who had made his own comic horror movie, The Fearless Vampire Killers (1967), thought Finch had the credentials to play Macbeth.