Ken Doherty survived a sleepless night, and the full force of a John Higgins fightback, before finally securing his place in the last four of the Embassy World Championship yesterday. The Irishman held on to win 13-8 and qualify for his first Crucible semi-final in five years.

It was remarkable in itself that Doherty had to fight so hard to get over the line, given that he had led 10-0 at one stage on Tuesday night.

Higgins' battling recovery to 10-6 suddenly threw the outcome into doubt, and it gathered further momentum when the Scot took the first frame yesterday with a break of 55 on his first scoring visit.

Higgins was also in first in the next frame with 56, but Doherty then struck a blow which both players later identified as the decisive turning point in the match, getting in to clear up with 63 and pinch it on the black for an 11-7 lead.

Massively relieved after halting the recovery, Doherty sealed the next frame with a 36 break after being handed a chance when Higgins attempted to extricate himself from a snooker. Higgins prolonged the match by running 82 in the 20th frame, but the Dubliner closed it out with the aid of an early 55 in the next.

"I was squinting at the scoreboard last night, thinking 'is this really happening ? Am I actually 10-0 up on John Higgins?'" Doherty revealed after the match. "John was in constant flow after that, and I was really starting to get a bit twitchy."

The 33-year-old also admitted that he had struggled to sleep on his return to the Marriott Hotel after the middle session.

"Just imagine all the headlines, saying things like 'the biggest collapse since Wall Street in the 1920s'. I couldn't stop thinking about it, especially after losing a frame on the black, and the second last one on the pink. How would I ever have got over it if I'd lost ?"

Doherty agreed that the frame he won to end Higgins' recovery had been the key to the match.

"I dug out a great clearance to go 11-7, the best I've ever made under pressure, and I think that stopped him in his tracks. For five or six frames before that, he hadn't looked like missing."

The opening session on Tuesday morning, in which Doherty had compiled a break of 107 and five others over 50, had been the foundation of his victory.

"I don't think I've ever played as well as that anywhere, except maybe when I beat Hendry in the final in Thailand two years ago. I knew it was in there somewhere, it was just a matter of bringing it out and I've been working very hard to do that over the last few months.

"I'm in great shape, and now that we're down to the semi finals, it's just the greatest buzz you can get."

Higgins admitted that he had been in despair when struggling to win a frame on Tuesday. "I was just trying not to be whitewashed, so when it got to 10-7 I was well pleased," said the 27 year old.

"But then I was well ahead in the next frame, Ken cleared up, and that knocked the wind out of my sails."

Doherty will be back on the table this afternoon for the opening session of his semi-final, over the best of 33 frames.

His opponent will be England's Paul Hunter who beat defending champion Peter Ebdon 13-12 in a dramatic match late last night.

Mark Williams became the odds-on title favourite after beating Stephen Hendry 13-7, to reach the semi-finals for the first time since he won the championship three years ago.

Williams' victory also ensured that he will return to the world number one position, when the annual ranking list is published next week.

The Welshman's opponent is Stephen Lee of England, who beat Hong Kong's Marco Fu - surprise winner over Ronnie O'Sullivan in the first round - 13-7 last night.