An exclusive bonus featurette that will be on The Dark Knight DVD has been released courtesy of The Guardian. The Dark Knight DVD will be available on December 9th.
In the first clip, Nolan and Christian Bale talk about the problems that Bruce Wayne/Batman faces at the beginning of The Dark Knight. He's helped clear up the streets of Gotham, but his success has spawned a wave of copycat vigilantes and incurred the wrath of the city's gang leaders. Bale talks about the "duality" of the character, and the fact that he's constantly at war with himself, battling to control his baser instincts.