John Michael Frederick Castle is an English actor. He is best known for his film and television work, most notably playing Bill in Michelangelo Antonioni's Blowup (1966) and Geoffrey in The Lion in Winter (1968). Other significant credits include Man of La Mancha (1972), I, Claudius (1976) and RoboCop 3 (1993). He is also a noted voice actor and has recorded an audiobook version of Vanity Fair (novel).