Webb first came to prominence as Ann Pornick in the original London production of "Half a Sixpence" opposite Tommy Steele, citing her first leading role as a career highlight. The playwright Beverley Cross's father George was the company manager on the production of "Stop the World, I Want to Get Off" and recommended his son audition Webb for the role. She was offered the role after thirteen auditions and later dubbed the singing voice of Julia Foster, her replacement for the film adaptation. Webb later commented of Foster, "She has quite a notable voice, so it's not too hard to pick it up."