Ding Junhui suffered a stunning upset at the hands of 41-year-old Irishman Leo Fernandez in the first round of the UK Championship in York.
The world number three and twice former winner of the title lost five frames in a row as Fernandez clawed back from 5-1 down for a famous 6-5 win.
Fernandez, the world number 130, had not won a match in four tournaments since returning from a 15-month ban after admitting playing a foul shot to facilitate a betting sting in a World Championship qualifier last year.
But he potted the pink and black to edge a tight decider and stun Ding, who first won the title when he beat Steve Davis at the age of just 18 in 2005.
Marco Fu avoided a similar fate as he beat veteran Nigel Bond 6-2, while Mark King was a quick 6-0 winner over Boonyarit Keattikun of Thailand.
Three-time UK champion John Higgins cruised to a 6-1 opening win over teenager and fellow Wishaw native Chris Totten.
Higgins scored three breaks over 50 on his way into the second round, after Totten had responded well to get his first frame on the board at 3-1.
Huge upset on day one!November 28, 2017
But Higgins' performance was eclipsed by two of his potential rivals for the crown as both Stephen Maguire and Kyren Wilson showed off some devastating form.
Maguire reeled off six consecutive frames to beat China's Yuan Sijun 6-1 - a run of six consecutive breaks over 50 including 127 and 128.
And Wilson also scored two centuries - and a third break of 96 - as he saw off Sean O'Sullivan by the same score.