Ruthie’s West End debut was in Cats, where she played a variety of roles including Jemima, Demeter, Jellylorum, Griddlebone and the leading role of Grizabella. Following Cats, she joined the world premiere cast of Miss Saigon. Ruthie created the role of Aphra in Children of Eden before appearances in Valentine’s Day, Divorce Me, Darling and Sisterhood. Ruthie then took over as Fantine in the West End production of Les Misérables. She was later invited to recreate this role for the acclaimed tenth-anniversary concert at the Royal Albert Hall as part of the “Dream Cast”, which was filmed for television.
Ruthie’s appearance in Crazy For You at the Prince Edward Theatre established her as one of the most popular stars in the West End. She was nominated for an Olivier Award for her performance and took the show to Canada where she played opposite Mickey Rooney. She starred as Roxie in the original London company of the revival of Chicago and has played both Roxie and Velma on Broadway and in 2018 became the only British actress to play all three female characters in the show when she played Mama Morton in the West End. She returned to television acting in 2021 by appearing as Miranda Evans in BBC soap opera Doctors.