Higgins' body was discovered after concerned friends broke into his Belfast flat having failed to contact him by phone. It is not known how long he had been dead inside the apartment.

The 61-year-old had been battling throat cancer for more than a decade. He also suffered from long-standing problems with alcohol and smoking.

Higgins died alone yesterday in sheltered accommodation in the Donegall Road area of Belfast.

It was a humble end for a former champion considered to be one of the finest snooker players of all time.

Taking up the sport at the age of 11, he won the All-Ireland and Northern Ireland amateur snooker championships in 1968.

After turning professional he became the youngest World Championship winner at his first attempt, beating John Spencer in 1972. The record was eventually beaten when 21-year-old Stephen Hendry claimed the trophy in 1990.

Higgins claimed the title for a second time in 1982.

A controversial figure, Higgins was banned from five tournaments and fined £12,000 (€14,349) in 1986 when he headbutted UK Championship tournament director Paul Hatherell.

In 1990, Higgins threatened to have fellow player Dennis Taylor shot and he was banned for the rest of the season after he punched a tournament director at the World Championship.

But despite his numerous fights and rows with referees, he continued to play the game regularly and appeared at the Irish Professional Championship in 2005 and 2006.

He inspired a generation of players to take up the game, with his influence seen in the style of later crowd favourites such as Jimmy White and Ronnie O'Sullivan.

Former World champion Steve Davis was among those paying tribute to a former rival.

Davis said: "To people in the game he was a constant source of argument, he was a rebel. But to the wider public he was a breath of fresh air that drew them in to the game.

"He was an inspiration to my generation to take the game up. I do not think his contribution to snooker can be underestimated."

As to his own encounters with Higgins around the table, Davis said: "He was quite a fierce competitor, he lived and breathed the game, very much a fighter on the table.

"It was a love/hate relationship with Alex Higgins. The thrill of playing him was fantastic, but the crowd that came along were not your usual crowd. They were much more noisy and you had to play the crowd as well. To many people in the 1980s he was the only player they came to watch."

"I used to be quite frightened of him as an individual, he could be quite vexatious. But on the snooker table, my admiration was immense."

Davis added: "No one player has ever been bigger than the game. But he brought a genius quality that possibly hadn't been seen before.

"He was one of two or three people I would put the word 'genius' to when it came to the table."

Former world snooker champion and commentator Dennis Taylor told the BBC: "I don't think you'll ever, ever see another player in the game of snooker like the great Alex Higgins."

And he said he had enjoyed some "terrific battles" against the sportsman, adding: "He was a very, very exciting player to watch. He just was totally unique."

Though Higgins "didn't look very well" towards the end of his life, he insisted: "He battled right to the end, did Alex, and that's what he did throughout his whole snooker career."

Snooker promoter Barry Hearn said Higgins would be remembered as the "original people's champion" and the man who transformed the popularity of the sport.

Mr Hearn said: "I have known him for nearly 40 years. He was the major reason for snooker's popularity in the early days.

"He was controversial at times, but he always played the game in the right spirit.

"We will miss him - he was the original people's champion."

Sean Boru, who ghosted Higgins' autobiography, said his death was an "inevitability" to those who knew him, but still came as a shock.

Mr Boru added: "The problem with Alex was that he knew he was a great talent but he didn't quite know how to work it.

"Alex was a frustrated genius. He had so much talent but he had very little outreach for it. He believed in himself a lot, but he also doubted himself a lot as well.

"He never really fully got the gist of the fame game."

Ronnie O'Sullivan described Higgins as a "legend" and "inspiration".

In a statement on his website, the three-times World Champion said: "Alex was one of the real inspirations behind me getting into snooker. He is a true legend and should be forever remembered as being the finest-ever snooker player."