Mark Shelby's UK Championship run ended by Hossein Vafaei

Selby, the winner of the tournament in 2012 and 2016, struggled to find his rhythm throughout and missed a chance to force a decider when he left Vafaei a cut to the middle in the 10th frame.

The 28-year-old Vafaei, who reached a career-best fourth round last year, held his nerve to sink a difficult green and brown and claim one of his most significant wins.

Defeat continued an underwhelming campaign for Selby, the seventh seed to lose in the tournament, whose best result remains his semi-final appearance in the Champion of Champions tournament earlier this month.

Vafaei's reward is a last-16 clash with Jack Lisowski, who fired breaks of 73, 83 and 66 as he cruised to a 6-1 win over another Chinese player, Xu Si.

Judd Trump overcame his "atrocious" UK Championship record to edge China's Xiao Guodong in a final-frame decider and also book his place in the last 16.

Despite winning the tournament in 2011 and boasting two subsequent final appearances, Trump has always struggled to deliver his best form in the second biggest tournament of the season.

History looked set to repeat itself as he struggled for long periods against Xiao, the world number 34, nudging in front for the first time in the seventh frame and missing a glorious chance to wrap things up before finally creeping over the line.

"My record here is just atrocious," Trump told the BBC. "Every game seems to go the same - I come well into the tournament then I go out there and I can't pot a ball.

"I don't know what it is. I feel good and I end up messing it up. I'm happy to get through because I love the prestige of this event and I'd have been devastated to be going home after the first game."

Xiao won the opener from behind and delivered a fine break of 118 in the third frame as his steady brand of snooker seemed to frustrate Trump, who had chances but continually failed to kill off frames in a single visit.

Trump looked to have wrested control when he got the better of a lengthy safety battle to move one frame away at 5-4, only to fluff a simple red in what should have been a match-winning clearance in the next, enabling Xiao to respond with an excellent 60 to force the decider.

This time it was Xiao who slipped up by attempting an ambitious safety that left a red open for Trump and the world number three retained his composure to fire a break of 88 and clinch victory.

Shaun Murphy came through a high-quality contest against David Gilbert, forcing a decider with a break of 133 before dominating that final frame to book his place in the last 16.