A new biography of the late AC/DC singer Bon Scott claims that the frontman died of a heroin overdose and not alcohol poisoning as has been previously believed. The singer was found dead in parked car in Dulwich, south London in February 1980. He was 33-years-old.

In Bon: The Last Highway, author Jesse Fink claims that Scott has already been dabbling with heroin and had previously suffered two earlier heroin overdose – one in 1975 and then again in 1976.

Drawing on extensive research and interviews, Fink questions the accepted belief that Scott died after a night of heavy drinking at London’s Music Machine club (now Koko).

“Basically he had a third overdose and this time it got him, that’s the conclusion I come to,” Fink told Australia’s News.com.

“Obviously if Bon ended up in hospital after two (over) doses of heroin he couldn’t tolerate it. In this book there’s two people who were there the night he died who believe he snorted heroin,” he explained.

“When he got to London the in thing was snorting smack, that was flooding London at the time, and it was brown heroin and very strong. All the characters linked to Bon in the last 24 hours of his life were allegedly associated with heroin. Heroin was a recurring theme in his death.”

Fink also found that in addition to heroin and his heavy drinking, Scott was also a user of Quaaludes, cocaine, marijuana.

He added: “He was a prodigious drinker. The idea that seven double whiskeys would put him in the ground seems a strange notion.”

Also in the book is the theory that Scott wrote most of the lyrics for AC/DC’s landmark album, Back In Black. Now the second best-selling album in the world, Fink questions whether Scott’s replacement in the band, Brian Johnson, actually wrote the album’s lyrics or whether they were Scott’s. The album was released just five months after Scott’s death.

Some of Scott’s former girlfriends who were interviewed for the book, claim to have seen the singer’s lyrics to ‘You Shook Me All Night Long’. One, Silver Smith, was in London when he died.

“Silver said Bon had called her and said he’d finished his work on Back in Black and that’s the reason he wanted to go out, which was the last night of his life,” Fink said. “It’s not like I’m the first person to ponder how much of Bon is on that album. It’s been talked about since the album was released. It’s never going to go away. I wanted to investigate as much as possible if Bon had anything to do with the lyrics for the album.”