A turnaround after the mid-session interval for Xiao Guodong, who has wrestled control of this all-China affair at the Crucible.

It all came down to the final two colours in the eighth frame and with Xiao in the box seat Zhou Yuelong left the pink into the middle pocket which his compatriot duly potted.

Xiao has established a two-frame cushion.

Mark Williams will take a three-frame lead into the second session of this match tomorrow.

Antoni Kowalski showed wonderful cueing to establish a 41-point lead, but then he bit off more than he could chew with a missed attempt on red when a straightforward safety shot was available.

He then made another mistake to open up the table, and up stepped Williams to take the lead.

Williams led by 23 with 22 points left on the table, but then he found himself snookered after a careless miss on the brown.

Kowalski couldn't take advantage though, and Williams takes the frame 73-45.

Steven Hallworth
Snooker commentator on BBC iPlayer

The most important ball on the table is the cue ball.

If you can master it, then the game becomes to simple for these players.

The margins in this game are so small.

Xiao Guodong is ahead for the first time the match.

A quality frame from the world number nine as he capitalised on routine missed black by Zhou Yuelong early on.

Xiao does briefly allow Zhou back to the table with the colours left but he cannot get a sniff of a pot and his compatriot clinically closed it out with the minimum of fuss.

Mark Williams potted the blue with enough power and spin for the cue ball to rebound off two cushions and set up a clear shot at a red. Brilliant shot.

With the reds all bunched up and with a 50-point lead, he played a safety shot to try and snooker Antoni Kowalski but didn't quite get it right.

Kowalski threaded the needle to pull off an impressive long pot and all of a sudden everything was set up to clear, but he missed red after the cue ball took a big bounce and rolled too close to the cushion.

Williams pots green to secure an overnight lead, before clearing up to win 74-35.

Image source, Getty Images

Antoni Kowalski tried a bit of an extravagant long pot on a red and the white ended up dropping in, and then made the exact same error on his next shot.

Mark Williams pulled out some very good safety shots, but had to look on in admiration as his young opponent took on and nailed an extremely difficult pot on a red into the middle pocket.

Kowalski moved 36-23 ahead, but clipped the jaw of the pocket to allow Williams to claim nice double.

Kowalski won the race to pot the final red, but a difficult shot on the yellow didn't drop in.

Williams potted it instead, and held up his hand in apology when the cue ball rebounded fortuitously for him to pot the green.

That frame could have gone either way, but it's Williams who takes the lead.

Another close frame between Zhou Yuelong and Xiao Guodong.

This time Zhou blundered on the final red in the corner pocket which opened the door for Xiao to take the frame.

Xiao potted the final red and then confidently worked his way through the colours to complete a ruthless clearance.

Back to all square.

Image source, BBC Sport

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A nip-and-tuck frame between Zhou Yuelong and Xiao Guodong which came out in favour of the former.

With just the colours left Xiao showed superb cue-ball control to knock the brown back into play when he potted the green.

However, with 13 left on the table Xiao rattled the pink into the jaws of the corner pocket.

Zhou then stepped up to pot the two remaining balls to level at 58-58 and the black was put back on the spot to decide the frame.

Xiao missed an ambitious double which left Zhou with a long long pot into the corner and he duly took it.

An uncharacteristic miss on the black by Mark Williams gave Antoni Kowalski the opportunity to compile a break of 68.

You could see the debutant wanted to claim his first Crucible century, but he clipped the jaws of the pocket with a red and had to settle for just winning the frame.

That's not a bad consolation mind you.

The 22-year-old almost lost his tour card earlier this week - now he is going toe-to-toe with a three-time world champion.

Mark Williams will have wanted to assert himself after the break, and he has done just that.

Williams makes a break of 49, before the pair trade several safety shots.

Antoni Kowalski made a few errors and Williams returned to the table to take the frame 78-0.

BBC iPlayer

If you're wondering where Mark Williams v Antoni Kowalski has gone, we're now over on BBC iPlayer.

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Michael Emons
BBC Sport at the Crucible

Image source, Michael Emons

It's a lovely sunny afternoon in Sheffield so in the mid-session intervals, some of the fans headed outside for a bit.

One of the more memorable sights outside the Crucible, as it has been for a number of years, are the hedges that have been trimmed to resemble a snooker player taking a shot (above).

Well, now you can get your picture with the human versions of that (see below). Earlier on it was proving to be a very popular fan interaction so expect plenty of comedy pictures from people that have been at the Crucible today.

Image source, Michael Emons

Antoni Kowalski levels the match before the mid-session interval.

Kowalski fouled early on to gift Williams six points, and the Welshman looked to be cruising to a 3-1 lead.

But Williams then hit the jaws of a pocket with red at 43-6 up to give Kowalski an unexpected way back in.

The Pole produced a break of 67 to take the frame 73-43.

Image source, BBC Sport

Table time in the previous frame clearly did Xiao Guodong a world of good.

Zhou Yuelong could only sit, watch and admire his Chinese compatriot as he rattled off the first century break of the match.

It was far from a straightforward table but after potting a couple of early tricky reds he completed the clearance with an impressive break of 122.

All square heading into the mid-session interval.

As we mentioned earlier, Antoni Kowalski is the 21st nationality to play at the World Snooker Championships

If you are wondering what the other 20 nationalities are...you're in luck.

We have the definitive list in a BBC Sport Ask Me Anything story.

Mark Williams made much lighter work of the third frame to win 85-21.

The veteran was going for a century break, but couldn't pot the green and settled for 85.

Unlike the first two frames of this match, Williams barely made a mistake and didn't give Kowalski a chance.

Much better from the three-time world champion.

Xiao Guodong has finally got himself some table time.

He compiled a break of 56 to put himself 37 ahead of Zhou Yuelong with 43 left on the table.

The frame appeared to be heading Xiao's way before he rattled a fairly straightforward red against the jaws of the pocket.

Zhou made a decent fist of it during a scrappy period but after he fouled at 64-33 with the score in Xiao's favour, and with multiple snookers needed, he conceded the frame.

Antoni Kowalski should be 2-0 up, but he lets Mark Williams in and pays the price.

Williams fouled early on, allowing his opponent to take a 34-0 lead, but finally potted for the first time 25 minutes into the match.

Kowalski had three chances to clinch the frame, but overthought a long pot on a yellow hanging over the pocket and ended up hitting the cushion too early.

The 22-year-old then superbly swerved around the black to escape a snooker and pot the yellow, but inadvertently snookered himself with the white right up against the pink.

Kowalski fouled five times in a row to bring Williams within three points of him, before the three-time champion levelled the score at 57-57 with brown, blue and pink left on the table.

A tactical battle followed before Williams finally took the frame.