Thomas was a British director, most active during the 1950’s and 60’s. He began his career as an assistant cinematographer and editor and then advanced to assistant director to David Lean. WWII started, and he joined the army where he received a medal. He returned to film after the war when he got a job in Rank Organisation, a British film company founded in 1937. Thanks to the job of editing promotional film trailers, he got a chance to direct his feature film debut Once Upon a Dream (1949). His first commercial success was the thriller The Clouded Yellow (1950). As a director, he is most remembered for a series of comedies about doctors: Doctor in the House (1954), Doctor at Sea (1955), Doctor at Large (1957) and Doctor in Distress (1963) starring Dirk Bogarde as well as Doctor in Love (1960), Doctor in Clover (1966) and Doctor in Trouble (1970). His other famous films include the comedy The Iron Petticoat (1956) starring Bob Hope and Katharine Hepburn film adaptations of The 39 Steps (1959) and A Tale of Two Cities (1958) as well as the political drama No Love for Johnnie (1961).