World number one Ronnie O'Sullivan crashed out of the World Championship in the first round after suffering a stunning defeat to amateur James Cahill.
In arguably the biggest shock in the tournament's history, Cahill held his nerve to beat five-time champion O'Sullivan 10-8 at the Crucible.
O'Sullivan was a prohibitive favourite before the match after a season which saw him win five titles and compile his 1,000th career century on his way to victory in the Tour Championship.
‼️The moment that shocked the snooker world— Sporting Life (@SportingLife) April 23, 2019
Amateur James Cahill beats five-time world champion Ronnie O'Sullivan...pic.twitter.com/jamcyBeQs6
The 23-year-old from Blackpool will face Scotland's Stephen Maguire in the second round.
A delighted Cahill 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."
The world number one, who had found time for a haircut between sessions, looked on course to set up a final-frame decider only to inadvertently pot a red as he broke open the pack from the blue.
That gifted Cahill the chance to claim the biggest win of his career and he held his nerve superbly with a break of 53 to win 10-8.
O'Sullivan, who looked completely out of sorts in the opening session, wasted little time in getting back on level terms by rattling in a break of 97 in the first frame of the morning to make it 5-5, with 10 frames needed for victory.
O'Sullivan, who has not lost in the first round since 2003, looked like taking the next frame as well before missing a red on a break of 48. Cahill took advantage in superb fashion, getting in with a three-ball plant and making a clearance of 88 to edge back in front.
O'Sullivan had the first chance in frame 12 as well but missed a black off the spot on a break of 34.
Cahill could only manage 22 in reply and both players had numerous chances before Cahill held his nerve to clear up to the pink and take a two-frame lead.
The amateur qualifier ran out of position on a break of 42 in frame 13 but O'Sullivan continued to miss chances and Cahill eventually did enough to get over the line.
That gave the 23-year-old an 8-5 lead at the mid-session interval and 15 minutes to ponder the fact that he needed just two more frames to cause a seismic shock.
Cahill's luck seemed to be in when he enjoyed an outrageous fluke on the black, rattling it in the jaws and seeing it travel twice across the table before dropping into the same corner pocket.
However, he then missed the red down the cushion and O'Sullivan took full advantage with a total clearance of 104 to reduce his deficit.
Despite the century, O'Sullivan still looked well below par and the 43-year-old needed several chances before eventually winning the 15th frame to trail 8-7.
O'Sullivan has previously complained of suffering from insomnia and did look tired as he sat in his chair between frames.
However, the five-time world champion produced a break of 89, which only ended when he called a foul on himself in potting a red, to get back on level terms at 8-8.
Cahill looked set to move back in front in the 17th frame, only to miss a straightforward red on a break of 62.
Just as O'Sullivan seemed poised to clear up and take the lead he missed the pink and, although it initially ran safe, a poor safety shot gave Cahill a second chance which he gratefully accepted.
The decider then saw O'Sullivan inadvertently pot that red and Cahill pounced to claim the shock win.