[1] She enjoyed success as a stage actress, notably in West End musicals such as the 1967 revival of The Boy Friend.
She starred alongside Michael Crawford in a production of Flowers for Algernon at the Queen's Theatre and features on the original London cast recording of the show.
[7][8] Kennedy took the role of Eliza Doolittle opposite Rex Harrison in a 1980 revival of the 1950s Broadway production of My Fair Lady.
[9] Her casting was initially challenged by Actor's Equity because she had been chosen ahead of more than 50 American actress finalists but Rex Harrison insisted that a British-born actress should take the part;[10] additionally, Mike Merrick, the show's producer, maintained her singing ability, her experience in musicals in London's West End and the authenticity she would bring as a result of her and her parents' lives in the London area made her uniquely qualified for the role.
[11] From the show's opening in New Orleans in September 1980, she continued in the role for nearly a year as it toured American cities.