Heath Ledger's Joker diary acts as a harrowing reminder of his commitment to the role

Heath Ledger's diary that he made when playing the Joker shows his harrowing commitment to the role.

Just months ahead of his death, the 28-year-old spoke about how his role in the Bob Dylan biopic, I'm Not There, and his famous role of the Joker in The Dark Knight caused an overthinking mind, which lead to insomnia and medication with Ambient and other sedatives.

The coroner's report into the Oscar winner's death concluded that Ledger died 'as the result of acute intoxication by the combined effects of oxycodone, hydrocodone, diazepam, temazepam, alprazolam and doxylamine'.

His death was ruled an 'accident' and was said to have been a result of 'the abuse of prescribed medications', combined with a possible chest infection that stopped him breathing.

Following his tragic and untimely death, German filmmaker Dag Freyer set about making a documentary: Too Young to Die: Heath Ledger , charting his demise and discovered his personal ‘Joker Diary' he made while preparing for the role.

You can watch a clip from the documentary below:

It contained notes and inspirations behind his acting choices, revealing a plethora of terrifying muses including hyenas, clowns, comic strips and Alex DeLarge from Stanley Kubrick's cult classic, A Clockwork Orange.

The diary was shared by Heath's dad, Kim Ledger, who confirmed that his son put himself into a self-imposed exile to really delve into the Joker's chilling psyche.

"He pretty well locked himself up in a hotel room for weeks. 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," Kim said.

One chilling page of the diary has the words, 'BYE BYE' scrawled in large, seemingly uncontrolled letters.

Ledger had finished his work for The Dark Knight in October 2007, however, the crew was in the process of editing when he died.

Warner Bros

Director Christopher Nolan said: "It was tremendously emotional, right when he passed, having to go back in and look at him every day.

"But the truth is, I feel very lucky to have something productive to do, to have a performance that he was very, very proud of, and that he had entrusted to me to finish."

Some people claimed that the twisted psyche of the Joker somehow played a role in his death, but that was shut down by his co-star Christian Bale, who recalled Heath saying: "[The Joker was] the most fun I've ever had, or probably ever will have, playing a character."

He was posthumously awarded an Academy Award for Best Supporting Actor, as well as accolades from the Golden Globes, Australian Film Institute, BAFTA and Los Angeles Film Critics Association for his role.