She will lead the audience in a "Mary Poppins" singalong. The specially arranged medley by Anne Dudley marks the 50th anniversary of the iconic Disney film title.

In a press statement, Henshall stated of making her Proms debut, "It's something I've always watched so to be a part of it is a total honor."

Henshall is currently appearing in the West End as Mrs. Wilkinson in Billy Elliot at the Victoria Palace Theatre. She has also appeared in the West End in Chicago, The Woman in White, Peggy Sue Got Married, Marguerite, Les Misérables, Oliver, Crazy for You, Cats and Miss Saigon. She won the Olivier Award for Best Actress in a Musical for She Loves Me. She has also been seen in Thea Sharrock’s production of Blithe Spirit at the Apollo Theatre. She has appeared on Broadway in Chicago and Putting It Together and Off-Broadway in The Vagina Monolgoues and The Other Woman, and in Ziegfeld Follies of 1936 and Stairway to Paradise at City Center.

She is joined by Sakari Oramo, Chief Conductor of the BBC Symphony Orchestra, leading his players for the first time in the world-famous finale of the festival.

The concert will also feature the world premiere of Gavin Higgins' BBC commission "Velocity" and a second world premiere, Arnold's "Peterloo" overture, in a new choral version with lyrics by Sir Tim Rice. For further details, visit http://www.bbc.co.uk/proms/whats-on/2014/september-13/15146.