According to reports in the Daily Mail, 22-year-old newcomer Hannah John-Kamen will star opposite Sally Ann Triplett as her stage mother.
The two actresses took part in the show's two prior workshops.
Triplett is currently playing the role of Donna in Mamma Mia! through Sept. 22. As a vocalist, she has twice been part of groups representing Britain at the Eurovision Song Contest earlier in her career. She has appeared regularly in the West End, starring as Reno Sweeney in the National's production of Anything Goes that transferred to the West End's Theatre Royal, Drury Lane, as Miss Adelaide in Guys and Dolls, as Grizabella in Cats and as Roxie Hart in Chicago, amongst numerous other credits.