The actor - who died aged just 28 of an accidental prescription drugs overdose in January - plays Batman's villain The Joker in the movie and is already being tipped for a posthumous Oscar for the role. The tribute at the end of the movie also acknowledges Conway Wickliffe, the special-effects technician who died last September in an accident involving a stunt car. The tribute reads: "In memory of our friends Heath Ledger and Conway Wickliffe." Meanwhile, the first review of Heath's performance in the film - a role which is said to have caused insomnia and led him to take the prescription medication which eventually led to his death - has been printed. Rolling Stone magazine critic Pete Travers writes: "I can only speak superlatives of Ledger, who is mad-crazy-blazing brilliant as The Joker. Ledger's Joker has no grey areas - he's all rampaging. He creates a Joker for the ages." The Dark Knight, also starring Christian Bale, Sir Michael Caine, Maggie Gyllenhaal and Morgan Freeman, is set for release worldwide at the end of July. Source:Tonight