Mercier had a long career on stage before her television career.
Donald Wolfit had talent spotted her and she toured with Wolfit's own Shakespeare company After the war, she worked in repertory theatre until 1951, receiving positive reviews from critics. One review said of her performance in
The Enchanted Cottage in 1948, "Sheila Rix is outstanding as the witch-like housekeeper." both at the
Whitehall Theatre itself, on tour to regional theatres, and in televised performances on BBC Television. Critics commented, "Sheila Mercier ..[is] up to the second in tempo and sense of fun;" In 1972, she was cast in the role she is best known for, the
matriarch Annie Sugden, one of the principal characters in the new British
soap opera Emmerdale Farm (later simply
Emmerdale). She appeared as a main cast member until 1994 with rare occasional appearances later including the funeral for on-screen son Joe in June 1995, along with screen husband
Amos Brearly. In 1979,
Hazel Holt in
The Stage wrote: "I never cease to admire the sheer consistency of Sheila Mercier's performance as Annie Sugden in Yorkshire's Emmerdale Farm. ... Every Tuesday and Friday, week in and week out she is never less than convincing." Mercier later reprised her role several times following the character's 1994 retirement. ==Personal life and death==