Stephens began acting as a teen in repertory theater and continued after studies at drama school. He joined the Royal Court in London in 1956 for important plays like "Look Back in Anger" and "The Crucible". Work in features began with parts which laid the grounds for future film roles: He made pirate Henry Morgan a robust Britisher in his US debut in the routine "Pirates of Tortuga", and he played the colorless, along-for-the-ride boyfriend of the heroine's domineering mother in the classic "A Taste of Honey" (both 1961). After joining the completely overwhelmed cast of the gargantuan "Cleopatra" (1963), Stephens played the nice, ordinary guy engaged to a woman desperately wanted by her loony ex-husband, the anti-hero protagonist of the landmark anarchic comedy "Morgan" (1966). Stephens and director Karel Reisz admirably refrained from making his role a dull, standardized comic villain, but David Warner and Vanessa Redgrave stole the acting thunder just the same.
Stephens' third wife (1967-74) was actor Maggie Smith, and the pair teamed for two films in which he played her lover. He was quite good as the sharp, lusty but feckless teacher colleague who witnesses "The Prime of Miss Jean Brodie" (1969) and was touching as the peripatetic protagonist's paramour in "Travels With My Aunt" (1972), but in each case Smith's zany comic elan was practically the whole show. His one major showcase came with his funny, profoundly troubled and yet stalwart sleuth in Billy Wilder's splendid "The Private Life of Sherlock Holmes" (1970). Subsequent character roles have been as military men ("The Duelists" 1977), artists ("Testimony" 1987), and titled Englishmen ("Bonfire of the Vanities" 1990). His best parts have came in offbeat fare, from "The Fruit Machine" (1988, as an opera star) to Kenneth Branagh's "Henry V" (1988, as Pistol).
Stephens' TV work has been modest but effective with the actor appearing mostly in highly prestigious miniseries such as "QB VII" (1974), "Holocaust" (1978), "War and Remembrance" (1988) and "Adam Bede" (1992). Much of his most important work has remained on the stage, with acting at the Royal Shakespeare Company and practically every other major theater running the gamut from "The Entertainer", "Saint Joan", "Royal Hunt of the Sun" and "Apropos of Falling Sleet" (which he also directed) to New York work in "Epitaph for George Dillon" and "Sherlock Holmes". In the 1990s, Stephens returned to the London stage and earned critical praise and awards for his performances as Falstaff and Lear. Father of actors Toby Stephens and Chris Larkin.