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 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 Defence Against the Dark Arts teacher during Harry Potter's second year at Hogwarts. He was played in the films by actor Kenneth Branagh.
