Clifford Parker Robertson III became a fairly successful leading man through most of his career without ever becoming a major star. Following strong stage and television experience, he made an interesting film debut in a supporting role in Picnic (1955). He then played Joan Crawford’s deranged young husband in Autumn Leaves (1956) and was given leads in films of fair quality such as The Naked and the Dead (1958), Gidget (1959) and The Big Show (1961).

He was born to Clifford Parker Robertson Jr. and Audrey Olga (nee Willingham) Robertson. Robertson Jr. was described as “the idle heir to a tidy sum of ranching money”. They have divorced when he was a year old, and his mother died of peritonitis a year later in El Paso, Texas. Young Cliff was raised by his maternal grandmother, Mary Eleanor Willingham as well as an aunt and uncle.

He supplemented his somewhat unsatisfactory big-screen work with interesting appearances on television, including the lead role in Playhouse 90: Days of Wine and Roses (1958). Robertson was effective playing a chilling petty criminal obsessed with avenging his father in the B-feature Underworld U.S.A. (1961) or a pleasant doctor in the popular hospital melodrama The Interns (1962). However, significant public notice eluded him until he was picked by President John F. Kennedy to play the young JFK during the latter’s World War II experience in PT 109 (1963).

Moving into slightly better pictures, Robertson gave some of his best performances: a ruthless presidential candidate in The Best Man (1964), a modern-day Mosca in an updated version of Ben Jonson’s “Volpone”, The Honey Pot (1967), and most memorably as a mentally retarded man in Charly (1968), for which he won an Academy Award for Best Actor. His critical success with Charly (1968) allowed him to continue starring in some good films in the 1970s, including Too Late the Hero (1970), The Great Northfield Minnesota Raid (1972), and Obsession (1976).

He starred in, directed and co-produced the fine rodeo drama J W Coop (1971) and, less interestingly, The Pilot (1980). He remained active mostly in supporting roles, notably playing Hugh Hefner in Star 80 (1983). More recently, he had supporting parts in Escape from L.A. (1996) and Spider-Man (2002).

Robertson died on September 10, 2011, just one day after his 88th birthday in Stony Brook, New York.