Hoult is currently filming the Superman sequel "Man of Tomorrow", and when the two projects couldn't be combined, HBO turned to Kit Harington instead.
Harington has already played Lockhart once before - the actor voiced the character in an audiobook recording of JK Rowling's second Potter novel, "Chamber of Secrets."
In the books, Gilderoy Lockhart is a famous author who becomes the Defense Against the Dark Arts teacher during Harry Potter's second year at Hogwarts. He was played in the films by actor Kenneth Branagh.
