Heath Ledger’s sister has come out to deny claims her brother was depressed while playing the Joker in Christopher Nolan’s Batman: The Dark Knight - a role he had finished working on only a few months before he tragically died.

Batman: The Dark KnightHeath Ledger's role as the Joker gave rise to controversy surrounding his death

The Australian actor died of an accidental overdose on prescription drugs on 22 January, 2008 aged 28 but his older sister, Kate, has refuted claims the actor suffered difficulties sleeping and other mental health issues while playing the DC comic book character role.

The Sun has reported on a new documentary called I am Heath Ledger, which is due to be released in the coming weeks and includes interviews with Heath’s friends, family and colleagues as well as footage Heath shot himself.

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Speaking at the premiere of the film at the Tribeca Film Festival in New York, Kate said the role - for which her younger brother won a Best Supporting Actor posthumous Oscar - was absolutely not taking its toll on him.

She said: "I was really shocked because that was him having fun. Every report was coming out that he was depressed and that [the role] was taking this toll on him, and we're going, honestly, it was the absolute opposite. It couldn't be more wrong.

"He had an amazing sense of humour, and I guess maybe only his family and friends knew that, but he was having fun. He wasn't depressed about the Joker."

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Documentary maker, Matt Amato said he hoped the film would be an antidote to the gossip that has surround the actor’s untimely death.

He said: "There are some really terrible things about Heath out there."

Tragic Heath had a daughter with American actress Michelle Williams in 2005, called Matilda Rose, who is now eleven.

Michelle and Heath split in 2007 and all Heath's fortune, around £13million, was left to Matilda in its entirety.