Snooker classics: James Cahill beats Ronnie O'Sullivan 10-8 at the 2019 World Championship

Having resumed with a 5-4 overnight lead following a closely contested opening session on Monday afternoon, Cahill kept his cool in the face of the inevitable O'Sullivan onslaught, producing a nerveless clearance of 59 to the pink to close out the match.

The 23-year-old from Blackpool told the BBC: "I believe I can beat anyone on the day."

Asked how he managed to hold his nerve to pot the final few balls to clinch victory over O'Sullivan, he replied: "I don't really know. I thought I was going to fall over at one point.

"I thought I'd be nervous when I went out there today but I wasn't. I was a bit tense in parts but I think I have shown quite a bit of bottle.

"It was nice to qualify and it was nice to beat Ronnie."

O'Sullivan turned in a ragged display, some brilliant break-building undermined by any number of unforced errors as Cahill sprinted into an 8-5 lead despite The Rocket kicking off the session with a fluent break of 97.

Cahill wasn't overawed, though, winning three frames on the bounce as O'Sullivan began to look increasingly jaded and frustrated, missing simple pots with alarming regularity, and the Crucible hummed at the prospect of one of the greatest ever shocks in the history of the World Championship as the players left for the mid-session interval.

O'Sullivan still had one final trick up his sleeve, however, and his now all-out-attacking approach saw him rattle off a break of 104 upon the resumption before he won the next two frames in double-quick time, a break of 89 drawing him level as Cahill finally began to feel the pressure.

Both players had their chances in frame 17 and despite Cahill making a break of 62, it was O'Sullivan who looked sure to edge in front when needing just pink and black for a potentially match-winning steal.

However, he missed the pink off the spot, bringing his break of 53 to an end, before Cahill finally closed out the frame with a brilliant cut-back black with the white under the cushion next to the bottom right-hand corner pocket.

O'Sullivan was again in first in frame 18 but was dealt a cruel, decisive blow when attempting to split pack from the blue, inadvertently potting a red upon cannoning the pack and handing Cahill the chance to clear for the match.

The amateur, who had just begun to show that the magnitude of the situation might at last be getting to him, held himself together superbly, a fantastic thin-cut pot on the final red leaving him with the colours at his mercy.

Yellow, green, brown and blue were negotiated without alarm and Cahill allowed himself a fist pump upon drilling in the the final pink before soaking up the warm ovation from a standing Crucible crowd as O'Sullivan made a swift exit from the venue and from the tournament.

"My limbs are feeling very heavy. I have no energy," he said after bowing out in the first round for the first time since 2003. "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.

"I tried to hang in there and get through this match and have a few days off before my next match.

"There are two ways of looking at it. One is, he has come here and played brilliantly. But I also left him some easy chances."

Related snooker content

• On this day: Robertson routs Murphy
• Crucible champions: Part Three
• Crucible champions: Part Two
• Crucible champions: Part one
• 1984 World Championship stands out
• Joe Johnson: The biggest shock
• White a People's Champion
• Crucible memories: O'Sullivan's finest hour
• Higgins prevails but Trump grows
• Snooker's pilgrimage put on hold