Amateur James Cahill produced arguably the biggest shock in Crucible history with a 10-8 victory over his “idol” and five-time world champion Ronnie O’Sullivan in the first round in Sheffield.

O’Sullivan was a prohibitive favourite for the World Snooker Championship before the match, following a season which saw him win five titles and compile his 1,000th career century on his way to victory in the Tour Championship.

But after recovering from 8-5 down to get back on level terms with the aid of breaks of 104 and 89, O’Sullivan crucially missed the pink when he seemed certain to snatch the 17th frame and Cahill took advantage to move 9-8 in front.

O’Sullivan then looked on course to set up a final-frame decider only to inadvertently pot a red when breaking the pack open from the blue, leaving Cahill to produce a nerveless break of 53 to seal a second-round meeting with Scotland’s Stephen Maguire.

After bowing out in the opening round for the first time since 2003, O’Sullivan admitted a combination of illness and his recurring insomnia had contributed to his sluggish performance.

“My limbs are feeling very heavy. I have no energy,” he said. “You come here and try to do your best but if you’re physically not 100 per cent it’s just one of those things. If you could take a magic pill to protect yourself from this stuff you would.

“It’s just life, it’s not the end of the world. I tried to give it my best, I tried my hardest and it wasn’t good enough. I tried to hang in there and get through this match and have a few days off before my next match.

Cahill celebrates after beating O’Sullivan 10-8
Cahill celebrates after beating O’Sullivan 10-8 (Nigel French/PA)

“If I feel better Friday I’ll be really disappointed, if I still don’t feel too great it probably wasn’t the worst thing that could have happened. It’s over, it’s done and now I can disappear and have a holiday and just enjoy the rest of the tournament.”

Cahill came through three rounds of qualifying to make his Crucible debut and the 23-year-old from Blackpool said: “I’m absolutely over the moon with that. I’m glad to hold myself together against the best player in the world on my Crucible debut, it doesn’t get any better than that.

“At the end when he starts coming back that’s what you expect against Ronnie, but I did a couple of good breaks to sneak frames back when it felt like he was just about to get on a bit of a flow and he’s under a lot of pressure himself, he doesn’t want to lose to me.

“You’ve got to believe you can beat anyone. I’ve got so much respect for Ronnie, he’s such a great player and my idol really, but there’s only so much respect you can have for these people because at the end of the day you have to go out and beat them.

“If you have too much respect for them I probably wouldn’t have cleared up at the end there. I don’t really know (how I did it). I thought I was going to fall over at one point.”

Ronnie O’Sullivan reacts after missing a pot
O’Sullivan reacts after missing a pot (Nigel French/PA)

Cahill lost his status as a professional in 2017 but has regained his place on the tour from next season and is determined not to rest on his laurels after beating O’Sullivan.

“I’m here to win the tournament,” added Cahill, who beat world number one Mark Selby in the opening round of the 2018 UK Championship. “I play every tournament to win otherwise I wouldn’t play. You can’t come to a tournament thinking you’re going to get beat… or what’s the point in playing?

“I’ve proved that I can play. I made the most centuries out of all the professionals in the qualifiers so the amateur thing doesn’t mean anything.

“I don’t have to prove anything now, I’ve got my two-year card, I’ve just beaten Ronnie, the world number one and I’m going to give it my all in my next game and see what happens.”

In the morning’s other match, 2015 champion Stuart Bingham raced into an 8-1 lead over Scotland’s Graeme Dott and needs just two more frames to reach the second round.

David Gilbert will face defending champion Mark Williams in the second round after holding off a fightback from qualifier Joe Perry to win just his second match at the Crucible in five appearances.

Gilbert saw his 8-4 lead reduced to just a single frame before a break of 52 took him to the verge of victory and the 16th seed held his nerve to seal a 10-7 win.

“I fell over the line in the end but we’ll certainly take it,” a relieved Gilbert said. “I didn’t feel I played that well but I struggled like mad and I’m delighted to come through.

“I woke up on Monday morning with severe man flu and struggled to concentrate but it’s the Crucible, you can’t just chuck the towel in.”

2019 Betfred Snooker World Championship – Day Four – The Crucible
Stuart Bingham edged through despite surrendering an 8-1 lead (Nigel French/PA)

The 2015 world champion Stuart Bingham survived a huge collapse from 8-1 up, including forfeiting one frame by committing three straight misses, to beat Graeme Dott, winner at the Crucible 13 years ago, 10-9.

World number six Mark Allen faces a battle to remain in the tournament after losing his first session 7-2 to China’s Zhou Yuelong, 29 ranking places below him.

Similarly Judd Trump, seventh in the world, is 6-3 down to Thailand’s Thepchaiya Un-Nooh, who won three of the last four frames in their first session to establish a healthy lead against the Masters champion.