Inside Heath Ledger’s ‘dark’ diary while playing the Joker shortly before death

Haunting images of a diary Heath Ledger kept after being cast in the role of the Joker offer an insight into the actor's mind shortly before his tragic death.

Film fans across the world agree that Ledger put on the performance of a lifetime when he played the antagonist in Christopher Nolan's The Dark Knight, but tragically the actor himself never got to see the impact he'd had.

Ledger died in January 2008, just a few months before The Dark Knight was released in cinemas, but pages from the diary he kept while filming offer more insight to his process and mindset behind the scenes.

In an effort to prepare for the intense role, Ledger admitted to Empire that he 'locked [himself] away' in a hotel room in London for about a month.

"[I] formed a little diary and experimented with voices — it was important to try to find a somewhat iconic voice and laugh," he said.

"I ended up landing more in the realm of a psychopath — someone with very little to no conscience towards his acts. He’s just an absolute sociopath, a cold-blooded, mass-murdering clown, and Chris has given me free rein."

Ledger's diary featured images of clowns. ((Broadview Pictures)

The diary features images and words that appear to have inspired Ledger, with photos showing different types of clowns and one image of a hyena, which may have inspired the Joker's eerie laugh.

Lists show Ledger trying to get into the mind of someone with 'no conscience', one of which is titled 'things that make me laugh'.

Underneath, the actor had listed morbid examples like 'land mines' and animals deaths, as well as more random objects including 'pencil cases'.

The final entry is among the most chilling, as it features the words 'bye bye' scrawled in large letters over the page.

Ledger's father, who obtained the diary after his son's death, later spoke about the dedication his son had given to the role.

The diary gave Ledger inspiration for the role. ((Broadview Pictures/Reddit)

He told press: "He galvanised the upcoming character. That was typical of Heath. He would do that.

"He liked to dive into his characters, but this time he really took it up a notch. He immersed himself in the upcoming character on every level."

Fans of the actor have shared their thoughts on his diary after pages from it were shared in a documentary about Ledger's life, with one person describing it as 'genuinely terrifying'.

They added: "Many actors that are method actors have a hard time coming out of a role and being themselves again. This was just on another level."

Prior to his death, Ledger had spoken about struggling with mental health issues as he experienced substance abuse issues and insomnia.

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