Northern Ireland's Mark Allen became the first major casualty of the Betfred.com World Championship as China's Cao Yupeng stunned the former semi-finalist.

Cao, only 20, will earn double his previous career winnings for reaching the second round after bridging a gap of 70 world ranking places to beat the current World Open champion 10-6, with a dramatic moment of defeat coming when Allen bizarrely potted the white along with the final black.

The 81st-ranked Guangzhou potter had registered his previous biggest win in the final qualifying round when he beat Leicester's world number 25 Tom Ford 10-9, a match in which Ford was docked an early frame for returning late from an interval.

Taking on Allen was an altogether different challenge, but the Asian under-21 champion gave a display which suggested his lowly ranking masks his real talent.

Allen has Crucible pedigree after reaching the 2009 final four and quarter-finals in each of the two years since.

But Cao was 5-4 up overnight following breaks of 70, 69 and 51, and a pair of classy centuries - 108 and 113 - steered him to the brink of a place in the last 16 at 9-5.

Allen responded with 101 to close the gap, and looked to have made it 9-7 when he cleared from blue to black.

There was a wicked twist though. As Allen roared his delight at potting an apparent frame ball, he had not spotted the white heading to a corner pocket, and when it dropped the victory was Cao's.