- In 2008, she beat hundreds of girls for a role in Oliver! at the Theatre Royal, Drury Lane in London, and remained in the stage production for a year.
- Said Keira Knightley acted "like a big sister" when Purnell played a younger version of the actress in the movie Never Let Me Go.
- Had her first onscreen kiss with Charlie Rowe.
- Named in 2010 by Screen International as one of its hot up-and-coming UK Stars of Tomorrow.
- Handpicked by Angelina Jolie to play a teenage version of the Oscar-winning actress in Maleficent.