Ledger's Joker 'terrifying', says director

'The Dark Knight' director Christopher Nolan has paid tribute to the dark acting skills of late actor Heath Ledger - branding his performance in the movie "terrifying."

The 'Brokeback Mountain' star filmed his final scenes as the Caped Crusader's nemesis The Joker for the forthcoming Batman film last year, just weeks before his tragic death in January.