In 1941 he began making documentaries and short features. When he was in the army, he made training films.

Hughes had three marriages, to two women. From 1946-1957, he was married to Charlotte Epstein. From 1970 to 1976 he was married to Cherry Price, with whom he had a daughter Melinda, an opera singer. The marriage was dissolved in 1976 and Hughes remarried his first wife in 1982. They were still married when Hughes died from complications from Alzheimer's Disease. He was living in a nursing home in Panorama City.

Hughes first film as Director was the "B" movie Wide Boy (1952). He did a short feature, The Drayton Case (1953), which became the first of Anglo-Amalgamated's Scotland Yard film series (1953-61), and several of the later installments including The Dark Stairway (1953) and Murder Anonymous (1955). He did Black 13 (1954) then made The House Across the Lake (1954) for Hammer Films, based on Hughes' own novel.

Hughes received notice for Joe MacBeth (1955) a modernised re-telling of Macbeth set among American Gangsters of the 1930s, but shot at Shepperton Studios in Surrey. He shared an Emmy Award in 1959 for writing the television play Eddie (for Alcoa Theatre) which starred Mickey Rooney.

He made some films for Columbia: Wicked as They Come (1956), The Long Haul (1957). He wrote High FLIGHT (1957) made by Warwick Films, producers Albert Broccoli and Irving Allen, who released through Columbia. For British TV he wrote episodes of Solo for Canary (1958).

For Warwick Films, he directed two films with Anthony Newley, Jazz Boat (1960) and In the Nick (1960). Warwick liked his work and hired Hughes to direct The Trials of Oscar Wilde (1960) with Peter Finch. It was well received, and Hughes favourite film because he did not make any concessions in its production.

Hughes wrote and directed The Small World of Sammy Lee (1963), based on Hughes' television play Sammy which had been broadcast by the BBC in 1958. Anthony Newley was the title lead in both playing a confidence trickster and gambler. He directed episodes of the TV series Espionage (1964).

He replaced Bryan Forbes, who in turn had replaced Henry Hathaway on Of Human Bondage (1964), satrring Laurence Harvey and Kim Novak. It was financed by Seven Arts who used Hughes on the Tony Curtis comedy Drop Dead Darling (1965). Hughes wrote episodes for the TV series An Enemy of the State (1965). Hughes was one of several Directors who worked on the James Bond spoof Casino Royale (1967).

He co-wrote and directed Chitty Chitty Bang Bang (1968) for Producer Broccoli. Although it was a success at the box-office, it received a negative response from critics who objected to its sentimentality. It was a project he did not enjoy working on. "The film made a lot of money, but that doesn't really make me feel any better about it. On the other hand, I've made pictures that got awards at Berlin and places, and didn't make any money, and that doesn't make me feel any better either". Irving Allen produced Cromwell (1970), a dream project of Hughes. It stars Richard Harris in the title role and Alec Guinness as Charles I, but was not a financial success.

Hughes faced financial difficulties in the late 1970s. He worked in the United States for the first time directing Mae West in Sextette (1978), it was her last film.

Hughes directed The Internecine Project (1974) for British Lion and Alfie Darling (1975), a sequel to Alfie (1966); they both flopped. He wrote and directed and wrote episodes of Oil Strike North (1975)

His final film was the slasher movie Night School (1981), the film debut of Rachel Ward.