Five-time champion Ronnie O’Sullivan won the last four frames of the session to haul level with Mark Williams at 8-8, and maintained the upper hand to prevail 13-10 in their quarter-final match at the World Snooker Championship.

But the thrilling contest might just be remembered more for William’s stunning act of sportsmanship in the dying moments.

Williams was staring at defeat, down 10-12, as he was about to hit the white. But he ended up accidentally touching the yellow ball with his hand.

While the referee failed to spot the foul, Williams owned up to it himself and surrendered his shot.

Watch the moment below, at two hours and two minutes in the video:

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Williams’s wonderful act of sportsmanship earned plenty of praise on social media:

Earlier in the tournament, O’Sullivan slammed the poor quality of snooker’s next generation after beating China’s Ding Junhui to reach the World Championship quarter-finals.

But after his 13-10 win against Ding, former world number one O’Sullivan said the current standard is so bad he would have to “lose an arm and a leg” to slip down the rankings.

O’Sullivan, 44, told the BBC: “If you look at the younger players coming through, they’re not that good really.

“Most of them would do well as half-decent amateurs, or not even amateurs they’re so bad a lot of them. A lot of them you see now, you think, cor, I’ve probably got to lose an arm and a leg to fall outside the top 50. So that’s why we’re hovering around, because of how poor it is down that end.”

(With inputs from AFP)