Gilbert & Sullivan's "HMS Pinafore" was performed in repertory with "Twelfth Night" and "Cymbeline" during Regent's Park's Open Air Theatre's season 2005. Scarlett played in HMS Pinafore the role of Josephine, the daughter of Captain Corcoran, Commander of HMS Pinafore, and who is in love with Ralph Rackstraw, an able Seaman. However, she is about to be betrothed to Sir Joseph Porter, K.C.B., First Lord of the Admiralty, who is visiting the ship together with a his sister, cousin, and aunt.
She was nominated for a Laurence Olivier award for this role in January 2006.