Power began her acting career on stage, appearing at a young age as Alison in a revival of the Slade-Reynolds Christmas musical, "The Merry Gentleman", at the Bristol Old Vic in 1959. After leaving RADA in 1966, she worked for 18 months at the Belgrade Theatre, Coventry. She had various roles in repertory theatre during her early career, and has since commented: "I got lots of jobs in rep, learning my craft and playing totally unsuitable roles—old ladies and the sort of stuff you did in those days."