By John Curtis, PA Sport

Mark Williams and John Higgins got their Embassy World Championship semi-final off to an explosive start as they ended the first session level at 4-4 after just 82 action-packed minutes.

Williams - already confirmed as next season's world number one - and Higgins were both in irresistible form and between them amassed seven 50-plus and one century break.

Higgins, the 1998 champion, is looking to avenge last season's 17-10 mauling at the same stage of the competition by Williams.

But the early signs are that this year's showdown in the best of 33 frame contest spanning four sessions will be a much tighter affair.

The quality was out of the top drawer from the first frame although Higgins was unfortunate when, having split the pack perfectly off the blue, he also potted a red.

That let in Williams who needed no second invitation to put together a break of 87 as he drew first blood.

Williams was also quickly amongst the balls in frame two but he broke down on 47 when he missed a long red with the rest - and Higgins was clinical in putting together a decisive run of 66.

The Welshman regained the initiative in the next with a break of 78 proving sufficient to put him back in front.

But Higgins reply was equally effective and breaks of 62 and 41 levelled the match by the mid-session interval with the whole four frames having lasted just 40 minutes.

The 'Wishaw Wizard' went ahead for the first time as two more half century breaks sealed frame five without Williams potting a ball.

Higgins was first amongst the balls in the sixth but missed a red over the right black pocket after he played the cue ball at a slow pace the full length of the table.

In stepped Williams with a 69 break to level matters again at 3-3 and a 48 in the next was sufficient for Higgins to regain the lead.

But Williams rounded off a sensational session in style with a break of 105 to ensure he went into Friday's second session all square.