Author DBC Pierre has won the 2003 Booker Prize for his first novel, black comedy Vernon God Little.
DBC Pierre won with his first novel Vernon God Little
The prestigious award is for the best novel of the last 12 months by an author from a Commonwealth country or the Republic of Ireland.
Also nominated were Margaret Atwood, who won in 2000, plus Damon Galgut, Zoe Heller, Clare Morrall, and bookies' favourite Monica Ali.
Pierre takes home a £50,000 cheque - as well as the bonus of the extra sales and publicity a Booker win gives.
Vernon God Little is about a high school massacre in Texas, and the head of the judges called it a "coruscating black comedy reflecting our alarm but also our fascination with America".
After his victory on Tuesday, Pierre told BBC News Online just how desperate he had felt when he began writing the book.
"In the end I was compelled to write," he said. "It was either that or take a length of rope and hang myself in the forest."
The 42-year-old writer is the third Australian to win the prize - now in its 35th year - following in the footsteps of Peter Carey and Thomas Keneally.
The chairman of the judges, Professor John Carey, said his team chose Pierre by a margin of four to one.
"The language is extremely vivid, most inventive, it's extremely exciting and very funny," he added.
Born Peter Finlay, his pseudonym refers to his nicknames, Dirty But Clean and Dirty Pierre.
At the weekend, he admitted to spending much of his life in a drug-induced "haze" - while past misdemeanours led to him selling a friend's house and pocketing the proceeds.
He told the BBC he would be spending his prize money paying off debts.
"This won't even touch my pocket," he told BBC Four.
"It is going to creditors. If they're not here now, I'm sure they will be in a minute."
He estimated the prize was worth "a third of what I owe in the world".
Another debut novelist, Monica Ali, had been the bookmakers' favourite to win with Brick Lane.
The other contenders were Oryx And Crake by Margaret Atwood, Notes On A Scandal by Zoe Heller, The Good Doctor by Damon Galgut and Astonishing Splashes Of Colour by Clare Morrall.