As an actress, Fennell is best know for her five seasons playing Patsy Mount on Call the Midwife, but she's also an acclaimed writer, with three episodes of Killing Eve credited to her. Unlike many of her co-stars, who are taking over roles from previous portrayers, Fennell will be the first person on The Crown to portray Camilla Shand, later Parker-Bowles, Prince Charles's first love and future second wife.