Batman's nemesis crowns dark tale :

Batman is played with brooding intensity by Christian Bale, while The Joker is reinvented by the late Heath Ledger as a twitching, evil psychopath smothered in gruesome, smeared make-up.

British-born Nolan says reviving The Joker was an important part of keeping the franchise exciting and "challenging" to the audience.

"Batman has always thrived on reinvention and it was very exciting to look in a very fresh way at a character who is almost as iconic as Batman himself," he says.
"The Joker was always designed to cut through the movie like the shark does in Jaws, and with his evil energy he tests all the other characters," adds the film-maker.
The Joker wreaks havoc across Gotham City with no apparent aim, leading to spectacular explosions, high-rise confrontations and a spine-chilling character study from Ledger.
Nolan said the actor developed into the role "organically" as the project progressed.