As Clark moved away from film and television, she returned to the stage. In 1954, she had starred in a stage production of "The Constant Nymph", but at the urging of her children, did not return to legitimate theatre until 1981, starring as Maria von Trapp in "The Sound of Music" in London's West End. Opening to positive reviews and what was then the largest advance sale in British theatre history, Clark—proclaimed by Maria Von Trapp herself as "the best Maria ever"—extended her initial six-month run to 13 to accommodate the huge demand for tickets and receiving a Laurence Olivier Award nomination for Best Actress in a Musical. In 1983, she took on the title role in George Bernard Shaw's "Candida". Her later stage work includes "Someone Like You" in 1989 and 1990, for which she composed the score, "Blood Brothers", in which she made her Broadway debut in 1993 at the Music Box Theatre, followed by the American tour; and Andrew Lloyd Webber's "Sunset Boulevard", appearing in both the West End and American touring productions from 1995 to 2000. In 2004, she repeated her performance of Norma Desmond in a production at the Opera House in Cork, Ireland, which was later broadcast by the BBC. With more than 2,500 performances, she has played the role more often than any other actress.