A Londoner convicted of murder over Brisbane's Whiskey Au Go Go nightclub bombing has died in the UK, robbing a new inquest of a key witness.
James Richard Finch was one of two men jailed for murder over the 1973 fire bombing that killed 15 people, but authorities have long suspected others were involved.
His death is a major blow as he was due to give evidence at a new inquest that will begin later this year.
"Counsel assisting was advised that since announcing the pre inquest conference, Mr James Finch has since died," coroner Terry Ryan was told during a pre-inquest hearing in Brisbane on Thursday.
Counsel assisting Stephen Keim later told AAP Mr Finch died earlier this year, and that he had been due to give evidence to the inquest electronically.
His own health issues and the pandemic prevented him returning to do so in person.
The only other person convicted of the club murders was John Andrew Stuart, and he died in 1979.
Finch spent his final years back in his homeland, after serving 15 years in Brisbane's Boggo Road Gaol and then being deported.
Rumours have persisted about the involvement of others in the bombing, which saw two 23-litre drums of fuel thrown into the foyer of the club. It was Australia's worst mass murder case until the 1996 Port Arthur massacre.
The new inquest was ordered following the trial over the murders of Barbara McCulkin and her two daughters 44 years ago.
Vincent O'Dempsey and Garry Dubois were convicted of those murders. The trial was told O'Dempsey may have been motivated over fears McCulkin could have implicated him in the firebombing.
O'Dempsey will be a key witness at the inquest, and the coroner can compel him to answer questions.