Biography: Julia Joyce (born 14 June 1998) is a British actress, known for her appearance as a younger version of Billie Piper's characters in Doctor Who ("Father's Day") and Mansfield Park, as well as for a role in Ruby in the Smoke. She is also the younger sister of the actress, model and Petits Filous advert star Lucy Joyce; Julia later went on to become the face of Petits Filous in her own right.