Maggie Smith as Daphne Castle
Daphne Castle is a non-canonical character created for the 1982 film Evil Under the Sun. She is an amalgamation of the characters Mrs Castle and Rosamund Darnley, from the original novel.
Daphne Castle runs a hotel on an island in the Adriatic Sea. The hotel in question is the former summer palace of the reigning King of Tyrania. He gave the palace to Daphne “for services rendered”. She is also an old friend of Kenneth Marshall, with whom she seems a bit flirtatious.
When Poirot is looking through the guestbook at the hotel, several signatures of famous guests can bee seen. Among them are: Ivor Novello, Fred and Adele Astaire, Cole Porter, Charlie Chaplin, Maurice Chevalier, and Marlene Dietrich.
After Poirot has solved the case, Miss Castle gets in contact with the king of Tyrania. He is very satisfied with Poirot's work and that he was so quick and discreet. The king decided to award Poirot with the Order of St. Gertrude the Inquisitive, 1st class.
Daphne is portrayed by actress Maggie Smith.