World Snooker Championship 2020: Jamie Clarke beats Mark Allen, Shaun Murphy out

World number 89 Jamie Clarke caused a huge shock by beating world number four Mark Allen 10-8 on a day of first-round upsets at the World Championship.

Welsh debutant Clarke, the lowest-ranked player in the tournament, turned around a 6-4 deficit against Allen, who made a record-equalling five centuries.

Earlier on Tuesday, Thailand's Noppon Saengkham stunned 2005 champion Shaun Murphy 10-4, converting a 6-3 lead on his second appearance at the Crucible.

Saengkham will face Mark Selby next.

Three-time champion Selby progressed after a 10-6 win over debutant Jordan Brown from Northern Ireland.

Former world number one Selby held a slender 5-4 lead over Brown heading into the second session, but progressed comfortably despite admitting some lapses in focus.

Since winning the last of his three world titles in 2017, his record in Sheffield has been poor, having failed to progress past the second round in the past two years.

He told BBC Two: "I am happy to win. The first round is always the toughest and you are always edgy, no matter who you are playing.

"It could have been better but I felt in patches I was close to playing really well. When I looked like I was going to kick on, I missed a silly ball and lost concentration.

"It was difficult out there to concentrate. There were two or three frames where I was fully focused and then I would lose it again."

Prior to this match, Llanelli's Clarke, 25, had made one semi-final appearance at a ranking event and lost in the first round at six tournaments this year.

And although Allen's barrage of scoring saw him make breaks of 136, 105, 122, 105 and 105, Clarke kept his cool by winning four frames in a row for an 8-6 advantage.

Allen hit back, but a break of 74 and snatching the 18th frame gave him the biggest victory of his career - on snooker's biggest stage.

Clarke said: "I am completely overwhelmed, I never, ever thought I would get to the Crucible in my life. As soon as I qualified I thought 'I am going to go out and love the experience and try to relax'.

"I stood up to him, he kept making breaks and I kept holding on to his coat-tails. My mentality was to try to keep close and pip him at the end.

"[Not having a crowd] helped me more than Mark, he relishes that and enjoys the atmosphere. I said to my dad and mum that it is better without a crowd as it takes away the atmosphere, which I am not used to."

Elsewhere, world number 60 Martin Gould produced a superb showing with four centuries to open up a commanding 7-2 lead over Scotland's Stephen Maguire, who reached the quarter-finals last year.

They play to a conclusion on Wednesday at 19:00 BST.

Former finalist Barry Hawkins leads Swiss debutant Alexander Ursenbacher by the same scoreline, heading into Wednesday's second session at 13:00 BST.

Murphy said his performance, in losing to Saengkham, had not been affected by the sudden death of his former manager and mentor Brandon Parker, whose funeral he attended in Portugal last month.

"I was very much below par across the whole match - probably the worst two days of my snooker years came together at the worst possible time," Murphy told BBC Sport.

"My form has been good this season with two titles and other finals, so this was a shock to me.

"And I can say that the build-up to the tournament had no impact. I came here wanting to honour Brandon Parker's memory.

"You dream of winning the title and dedicating it to him and things like that. But I would never dishonour him by saying that has caused me a problem."

Saengkham estimated up to one million people will have watched the match in a country whose appetite for snooker owes much to former world number three and two-time Crucible semi-finalist James Wattana.

"James taught me everything - how to come here and speak the language," said Saengkham. "He taught me how to get through because for an Asian player to come to the UK is difficult.

"I felt a lot of pressure but I just tried to concentrate on the table and not think about all those people watching me.

"For the past three or four days, I have turned my phone off and not done anything on the internet. If I turn my phone back on, it will be too much pressure with all the messages."

Six-time world champion Steve Davis: "Noppon played so well, and was knocking in a lot of balls very confidently, but it could have been a completely different match with Shaun 1-0 up when he missed a ridiculously easy red in the second frame. Things went weird for him from there and it started to look like he wasn't concentrating fully."

Seven-time world Stephen Hendry: "Noppon's clearance to win the match was stunning. We've seen top players go 9-4 up and all of a sudden get scared of the winning line. He looked so composed and he's beaten one of the best players of the season 6-3 and 4-1 in two sessions which is very impressive."