Beloved UK actress Haydn Gwynne passed away October 20 one month after Ms. Gwynne was forced to withdraw from Stephen Sondheim's Old Friends in London. She was 66.

Her death was confirmed by her longtime agent team, Markham Froggatt & Irwin, who gave the following statement:

“It is with great sadness we are sharing with you that, following her recent diagnosis with cancer, the star of stage and screen Haydn Gwynne died in hospital in the small hours of October 20, surrounded by her beloved sons, close family and friends. We would like to thank the staff and teams at the Royal Marsden and Brompton Hospitals for their wonderful care over the last few weeks.”

Ms. Gwynne's passing is a shocking turn in a lengthy career filled with dramatic highs. Beginning her career as a supporting lead in various television programs, including Peak Practice, she became a familiar face on the U.K. boards, appearing on bother regional and London-based stages, as well as with the Royal Shakespeare Company.

On the stage, she starred in Tom Bolton's influential production of Hedda Gabler, Richard Cheshire's Way of the World, played Billie Burke in the West End production of Ziegfeld, and starred in the original West End company of City of Angels. But it was Billy Elliot the Musical that would immortalize her for a generation.

Ms. Gwynne played Mrs. Wilkinson, the dance teacher, in the vastly successful coming of age musical. For her efforts in the West End production, she was nominated for an Olivier award, and for her reprisal of the role on Broadway, she received the Outer Critics Circle award, the Theatre World award, and the Drama Desk award, in addition to a Tony nomination.

In the 2010s, Ms. Gwynne starred alongside Tamsin Greig in the musical Women on the Verge of a Nervous Breakdown, played Margaret Thatcher in Peter Morgan's The Audience, and enjoyed a star turn as Mrs. Peacham in Simon Stephens' adaptation of Bertolt Brecht's and Kurt Weill's Threepenny Opera for the National Theatre in London. Simultaneously, she made another series of television appearances on programs as diverse as Ripper Street and The Windsors, playing Camilla, then Duchess of Cornwall in the latter.

In the past two years, it appeared that Ms. Gwynne was building up to another period of peak career activity. She closed the London revival of Anything Goes as Evangeline Harcourt, played Susan Hussey in the fifth series of The Crown, and starred as Pam Lee in The Great British Bake Off Musical, all over a period of 18 months.

Ms. Gwynne was to be one of the starring members of the Stephen Sondheim's Old Friends concert production currently playing in London following her remarkable performance in the original one-night-only tribute, but was forced to withdraw in September due to her ailing health.

She is survived by her partner, Jason Phipps, and their sons.