Ledger was approached to play Batman

Heath Ledger was asked by director Christopher Nolan to play Bruce Wayne in 'Batman Begins', it has emerged.

But Ledger, who was instead cast in the Oscar-winning role of the Joker in 'The Dark Knight', turned the part down.

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“He was quite gracious about it, but he said, 'I would never take a part in a superhero film',” Nolan told The Playlist.

But after explaining to Ledger what he was planning for the films, including sending him the novel 'A Clockwork Orange' and books on the paintings of Francis Bacon, Ledger decided to come on board.

“I explained to him what I wanted to do with 'Batman Begins' and I think maybe he felt I achieved it,” he said.

“Heath spent months and months [preparing], we cast him even before the script was written so he had a very long time to obsess about it, think about what he was going to do, to really figure it out.”

Nolan also spoke about Ledger achieving the voice of the character.

“It was so unpredictable,” he said. “The voice was certainly scary because it would shift in pitch. You never quite know which way the pitch is going to go with the voice.

“Just as the physical movements were [unpredictable], you didn't know what he was going to do with his hands, the way he moved, it was always a surprise. The actual tone of his voice was a surprise too. Sometimes threatening and sometimes more sing-song and light.”

Ledger won the Best Supporting Actor Oscar posthumously for the role. He died in 2008, aged 28.