Four-time winner Mark Selby crashed out in the first round of the World Snooker Championship after a late-night 10-8 defeat to qualifier Ben Woollaston.
Selby had edged the opening session of the first-round match 5-4 against Woollaston - a fellow Leicester native and practice partner.
Woollaston, though, started a fightback by taking the first two frames on Thursday evening's resumption before Selby won a safety battle in frame 12 to level up at 6-6.
Selby then showed his frustration at losing the 13th frame - sending the yellow ball up the table after conceding.
World No 44 Woollaston further extended his lead before Selby reduced the deficit again after edging a scrappy 15th frame.
After Selby again failed to make a significant break in the next, Woollaston produced a run of 49 to leave the former champion needing snookers before closing out the frame to move one away from victory at 9-7.
After two re-racks at the start of the 17th frame, with Woollaston failing to make the most of his chances at the table, Selby eventually crafted a classy break of 81 to stay alive in a match which had passed the seven-hour mark.
A tense 18th frame saw unforced errors from both men, with Woollaston sending a pink against the jaws of the middle pocket when seemingly set to build a match-winning break.
Selby had opened up a 24-point lead, but then missed a pot which allowed Woollaston back in to edge in front with the final red remaining.
A foul from Selby then left a free ball, with Woollaston pushing on to the colours, leaving the former champion needing two snookers.
After Selby - who lost in the first round last year - left the blue on to the middle pocket, he offered his friend a handshake, as Woollaston marked the biggest win of his career.
Speaking just after his defeat, Selby said: "I didn't deserve to win. Ben played some great stuff, his safety was unbelievable at times but I still had my chances. It was pathetic really from me, to play like that is disappointing.
"It's the same old story, I try too hard and stop myself from playing. I love Ben to bits, I've known him for years. I grew up with him and have seen him progressing."
Woollaston goes on to face Si Jiahui in the last 16. "I'm in shock really," he said after.
"I never thought this day would come, winning a match at the Crucible, and against Mark, who except for Ronnie O'Sullivan is probably the king of the Crucible in recent times. It's an amazing win for me."
Earlier on Thursday, former champion Luca Brecel had overcome a big deficit to beat Ryan Day and book a last-16 clash with Ding Junhui.
The 2023 world champion appeared to be in danger of joining last year's winner Kyren Wilson in crashing out in the first round when he found himself 5-1 down to Welshman Day during the first session.
But the Belgian won the final three frames on Wednesday to make it 5-4 and get himself right back in the match.
A century from Day in the opening frame of the second session put Brecel on the back foot once again, but he won three successive frames twice more on Thursday afternoon to close out a 10-7 victory.
Four-time world champion John Higgins is locked at 4-4 with China's Xiao Guodong after a nip-and-tuck start to their last-16 encounter, which will resume on Friday afternoon.
Chris Wakelin made a lightning-quick start to his second-round match against Northern Ireland's Mark Allen, racing into a 6-2 lead.
