�Batman Begins� director Christopher Nolan has promised that new �Joker� actor Heath Ledger will deliver a very different character then audiences are accustomed to.

Speaking to Mean magazine, Nolan explained how a one off comic named �The Killing Joke� has been the main source of inspiration for Ledger�s Joker.

Nolan said of the darker Joker: �I would certainly point to The Killing Joke but I also would point very much to the first two appearances of the Joker in the comic.

�If you look at where the Joker comes from there's a very clear direction that fits what we're doing very well.�

Nolan also said that the title of the new film �The Dark Knight� was the key to what the new film was all about.

He added: �The title has been chosen very specifically. It's quite important to the film.�

�The Dark Knight� is out sometime next year.