After more late night drama at the Crucible on Wednesday, Joe Perry pulled off a suprise 13-12 victory over Stephen Maguire to reach the semi-finals of the World Snooker Championship.

Perry is playing Ali Carter in the semi-final over 33 frames for the right to face Ronnie O'Sullivan or Stephen Hendry in the final.

Maguire struggled to impose himself on this contest. At certain points he threatened to pull away, but could not shake off Perry. The Glaswegian admitted that he struggled to handle the pressure at the business end - just as he did last year when he let a lead slip against John Higgins in the semis.

Trailing 8-7 going into the final session, Maguire nicked the first on the pink then came from 63-0 down to add the next with a 70 to go 9-8 ahead.

Perry battled back to win the next two with 63 and 55 then Maguire rolled in a 60 for 10-10. Perry opened frame 21 with a 53 but Maguire made a superb 63 clearance to take the momentum. Crucially, Maguire had a kick on the blue off the last red at 45-54 in frame 22, Perry clearing to level the match.

In the next, Maguire missed a red on 50 but Perry failed on the last yellow on 43, allowing his opponent to take it on the pink.

A scrappy 24th went the way of Perry to make it 12-12 as the Crucible crowds were treated to another thriller. Perry took control of the decider with a run off 33 before failing to split the pack off the blue.

Maguire had one real chance but missed his opening red, and Perry took full advantage with a 54.

The result means that O'Sullivan will be the official world No. 1 next season, and becomes the first player to hold the top spot on three separate occasions.

Semi-final (first session): O'Sullivan vs Hendry 4-4.