Maguire, who won this tournament in 2008 and was the 2004 UK champion, opened up a 2-0 lead with breaks of 76 and 57 enough to subdue O'Sullivan early on.

The three-time world champion showed his class however, with a break of 88 enough to win the third frame and a 60 sufficient to level the match after Maguire missed a red into the middle pocket.

A break of 79 restored the Scot's lead but a missed blue in frame six prompted a spectacular 102 response from O'Sullivan, who concluded the frame by blasting in the final black.

Maguire moved in front again but a 48 from O'Sullivan forced the decider. Maguire went on an early run to 29 before overstretching for a black, before a 41 put O'Sullivan in the driving seat.

Maguire could not get position from the final red to take on the black or pink, so a re-spot was the best he could hope for and after clearing the colours, he rode his luck to see out the match.

Trowbridge cueman Lee secured a fourth ranking event semi-final appearance out of the last five with his triumph over Trump.

Trump took a 2-0 lead with an impressive 92 break but Lee stormed back to lead 4-2, with a stunning 113 bringing him level at 2-2.

Last year's World Championship finalist Trump cleared to the pink to win frame seven but a break of 96 sealed it for Lee.

The evening session will feature home favourite Ding Junhui against Ali Carter, with Neil Robertson taking on Peter Ebdon in the other quarter-final.