The pair slugged it out for 11 frames before Doherty emerged victorious to set-up a semi-final against Stephen Hendry or Jimmy White.

“I’m disappointed to lose but you can’t take it away from Ken,” said O’Sullivan, who has only one Masters title to his name from 10 visits to the Conference Centre.

“He made a great break in the last and deserved to win.

“I thought I played the wrong shot to let Ken back in and that’s a lesson I can take away from here. Hopefully, I will never do it again.

“It was a good match and a tactical game. You have got to take the positives from the matches like that and I think I’m going in the right direction.”

The pair had not met since O'Sullivan's 10-1 victory in the 2001 UK Championship final at York.

And it soon became evident the Irishman was going to make his one-time Ilford Snooker Centre club-mate work hard for a victory.

Three times Doherty took a one-frame lead with a top break of 99 in the fifth. Each time O’Sullivan resisted the temptation to attempt outrageous shots and his patience was rewarded.

His effort of 72 levelled the contest at 3-3 and a 55 tipped the balance his way in the seventh.

But Doherty, twice a B&H runner-up, is desperate to make it third time lucky on Sunday night.

He reeled off a double of his own to move 5-4 clear. Again O’Sullivan responded positively to set-up a deciding frame much to the delight of a 1,500 crowd.

Both missed early opportunities before O’Sullivan surged 37-8 in front.

Even a missed red into a top pocket did not prove costly. Instead, a loose safety shot moments later was more damaging.

It enabled the 1997 world champion to compile a superb 59 break that left the Englishman requiring two snookers.

“It’s probably the best break I have made this season,” said the 33-year-old world number five.

“Probably one of the best of my career given all the pressure.

“I just seemed to get on everything perfectly though I hadn’t expected to get another opportunity.

“There was a fantastic atmosphere out there, a real buzz. It’s what you dream about when you are growing up-a big occasion, big matches in a big competition.

“And this was one of them. It was also great to win another deciding frame. That’s three in a row now.

“I knew I was going to be up against it but I hung in there well and I’m delighted to still be in contention.”