Robert Easton: Actor who was also dialogue coach to a host of stars

Although he clocked up dozens of screen appearances over more than half a century, the American actor Robert Easton's greatest claim to fame was as dialect coach to some of film's biggest stars. He called himself the Henry Higgins of Hollywood, after the professor of phonetics in My Fair Lady. Perhaps most successful was his contribution to Forest Whitaker's performance as Idi Amin in The Last King of Scotland (2006); Whitaker's East African accent and use of Swahili combined with his large physical presence and chilling portrayal of Amin's menacing stare and unnerving mood changes to win him a Best Actor Oscar.

Easton had shown his range in coaching Gregory Peck, first as the Nazi concentration camp doctor Josef Mengele in The Boys from Brazil (1978), then as Abraham Lincoln in the television mini-series The Blue and the Gray (1982). When Laurence Olivier played Douglas MacArthur in the 1981 drama Inchon, Easton was on hand to assist with the accent. The US Secretary of State Alexander Haig, who had been an aide to MacArthur's chief of staff, told Olivier that the general spoke like WC Fields, so Easton coached him in that comedy actor's speech patterns. Unfortunately, he could do nothing about Olivier's ludicrous make-up, including a wig and false nose, and Inchon became the biggest loss-making film of 1982. More happily, Easton worked with Olivier when he played a Detroit car-company's founder in The Betsy (1978), based on the Harold Robbins novel.

When he was asked to coach Robert Duvall in a Virginian accent for the role of a Confederate commander in the 2003 film Gods and Generals, he asked: "Which one? There are 12." He also helped Al Pacino sound like a Cuban in Scarface (1983), Arnold Schwarzenegger speak Russian English in Red Heat (1988), Liam Neeson adopt a Kentucky drawl in Next of Kin (1989) and Ben Kingsley master the gruff tones of a New York mobster in Bugsy (1991), as wellas working with Charlton Heston, Patrick Swayze, Robin Williams and Anne Hathaway. In Britain, Easton was familiar to fans of Gerry Anderson's Stingray (1964-65) as the voices of the unflappable navigator "Phones" and the villainous Agent X20.

Born in Milwaukee, Wisconsin in 1930, Robert Easton Burke was seven when he moved to San Antonio, Texas with his mother, following his parents' divorce. In an attempt to combat a stammer he adopted the local accent and learned to speak more slowly. He was confident enough to take part in the radio show Quiz Kids (1945) at the age of 14, followed it with other radio programmes and, in 1949, landed his first bit-part in a Hollywood film, as a parking valet in the crime thriller Undertow, which included Rock Hudson as a detective. In the same year, he briefly studied at the University of Texas.

After an appearance in the John Huston-directed Civil War drama The Red Badge of Courage (1951), the 6ft 4in actor legally changed his name, dropping his father's surname to become Robert Easton – sometimes credited as Bob Easton. He was rarely out of work and soon in demand on television, too, taking one-off roles in series such as The Adventures of Superman (1953) and Gun Law (1955) before a run as the college student Brian McAfee in The George Burns and Gracie Allen Show (1957-58).

To branch out from the country-bumpkin roles in which he was becoming typecast, Easton decided he must learn other accents. He studied phonetics at University College London, which enabled him to add European dialects to his repertoire. While there, he acted alongside Steve McQueen in the film The War Lover (1962), about the effects of combat on young men at a USAF base in Cambridgeshire, and appeared in the comedy Come Fly with Me (1963). He also had a small role in the television series The Saint (1962).

On returning to the US, Easton soon began to profit from his knowledge of accents and dialects. He worked with Charlton Heston in his role as General Gordon in the epic adventure Khartoum (1966), and assisted other actors over the next 45 years in films such as The Molly Maguires (1970), The Neverending Story (1984) and Good Will Hunting (1997).

Easton coached Natasha Richardson when she played the eponymous abducted socialite in Patty Hearst (1988) and Drew Barrymore for her role as the "Long Island Lolita" in the television film The Amy Fisher Story (1993). In the same capacity, he worked on TV productions such as Jacqueline Bouvier Kennedy (1981), North and South (1985) and Kane & Abel (1985). A particular triumph was his tutoring of the Japanese actress Yôko Shimada, who did not know a word of English, for her English-language performance in the mini-series Shogun (1980), for which she won a Golden Globe.

Easton played a Klingon judge in the film Star Trek VI: The Undiscovered Country (1991) and the mayor in the 1993 big-screen version of The Beverly Hillbillies. Shortly before his death, Easton – who taught at the University of California Los Angeles and the University of Southern California – helped John Travolta to prepare for his role as a former Serbian soldier in the forthcoming film Killing Season.

Robert Easton Burke, actor and dialect coach: born Milwaukee, Wisconsin 23 November 1930; married 1961 June Grimstead (died 2005; one daughter); died Los Angeles 16 December 2011.