The result is even more remarkable considering Donaldson had won just one match this season before the match, a 6-2 victory over John Astley in the first round in York.

But the Scot held his nerve to claim the biggest victory of his career.

"I did not do that much wrong," said Selby.

"Scott played absolutely unbelievable and to play like that on the main stage is remarkable.

“I have been saying all season, everyone seems to be overperforming against me.

"Every time I had a chance, I needed to make something but every time he had a chance the balls were set for him.

“He took them and closed the match out really well."

Defending UK champion Selby took the opening frame courtesy of a 68 break and extended his advantage before the 23-year-old halved the deficit with a wonderful run of 88.

Donaldson won the next two to nudge ahead for the first time in the match before Selby levelled following another half-century run.

The Scot maintained his composure and rattle off the last three frames to earn the shock win after compiling breaks of 90 and 77.

He advances to the third round of the competition for just the second time in his career.

"I am calm, it is another win for me, I do not care who I play," said Donaldson. "I had good chances in the balls and I capitalised on them.

"It has been well documented that I have not won a game this season, but I have had a lot of cue problems. I am happy with it now and it is playing better than before."