While performing at London's Royal Albert Hall in 1944, Clark was discovered by film director Maurice Elvey, who cast her, at age 12, as precocious orphaned waif Irma in his weepy war drama "Medal for the General". In quick succession, she performed in "Strawberry Roan", "I Know Where I'm Going!", "London Town", "Here Come the Huggetts", "Vote for Huggett", and "The Huggetts Abroad", the second, third, and fourth of four Huggett Family films based on a British radio series. Although some of the films she made in the UK during the 1940s and 1950s were B-films, she worked with Anthony Newley in "Vice Versa" (directed by Peter Ustinov) and Alec Guinness in "The Card". She also had a small role in the aforementioned "I Know Where I'm Going!" (a Powell and Pressburger feature film generally regarded as a masterpiece).