Maguire made a brilliant 132 in the 14th

The 2004 winner went into the final session of his match with a 5-3 lead before taking the next two frames and allowing Williams to score just two.

Williams made a 52 break to take the next before Maguire rattled in 53 to make it 8-4 and although he was pegged back again a 132 break sealed his win.

Maguire will now play Shaun Murphy who recorded a 9-7 win over Ding Junhui.

Highlights: Maguire 9-5 Williams

That encounter was a scrappy and tense affair throughout, with both players having shared the eight frames of the first session.

In fact such was the cautious approach adopted by the fluent potters that neither managed a break over 50 in the first three frames.

Murphy then showed a glimpse of the form that helped him to the 2005 World Championship with a patiently constructed 52 to make it 2-2 before Ding, 20, hit back with a 62.

The Chinese youngster should have made it 4-2 but broke down after a break of 59 allowing Murphy to rattle in 49 and steal the frame by a point, before the pair shared the final two frames of the session.

It was tit-for-tat in the next six of the final session, with Murphy scoring a 68 and 54, and Ding making a 69 and 65.

But then Murphy, the provisional world number one, clinched the crucial 15th before calming his nerves to make a break of 74 and secure victory.