Trump's fourth of this match, and his 107th of the season.

A break of 116, the equal-largest of this semi-final, moves Judd Trump to three frames from victory.

But Mark Williams still only needs one...

Judd Trump is potting well, and a delicate red into the middle right will stop Mark Williams coming back to the table.

I hope you're as engrossed in this match as I am. Phenomenal sport.

Image source, PA Media

Judd Trump needs every shot from here to be practically perfect in every way, and so far he is playing the role of a snooker version of Mary Poppins very well.

A cannon following a pink opens up the red nicely. He has a big chance here.

No! Mark Williams has the reds split and poised, but makes a poor contact and misses to the left middle.

Let-off for Trump.

Steve Davis
Six-time world champion on BBC Two

You never know, slowly it can turn. The tide sometimes does. But you always feel with Mark Williams that he will get a chance and, even if it's a tactical frame, he knows how to get over the line.

Judd Trump has made a few rocky starts to frames this evening, and he's done it again as he inadvertently leaves a red over the pocket for Mark Williams to tuck away with a long pot.

Trump returns to his seat, fearful he will not rise again in this tournament.

Dennis Taylor
1985 world champion on BBC Two

You can't blame Mark for taking that very difficult red to the middle pocket. If it goes in, he could have won the match.

Judd Trump just has to keep putting one foot in front of the other.

He's back to within three frames of Mark Williams.

Mark Williams cannot capitalise on that mistake, and Judd Trump is back at the table.

It's not a clean frame by the world number one by any means, but he is still the clear favourite in this one.

Ah, Judd Trump pushes the cue ball too far on a regulation red and he's left himself without an easy pot on a colour.

He has to use the rest and try to cut the black very fine - and despite an excellent attempt, Trump catches the near jaw of the pocket and that's end of break.

After the tense start, the balls are sitting up nicely for Judd Trump now in this frame.

A reminder that he has to win every frame remaining in order to triumph in this match.

Image source, PA Media

After back-to-back century breaks before the interval, this frame is a whole lot more cautious as the players exchange safety shots.

Mark Williams then misses a difficult attempted red to right middle, and Judd Trump responds with an excellent long pot.

Mark Williams comes back down the table off the brown, but his attempt at spreading the reds doesn't quite pay off - only three split from the pack.

Williams plays safe, and Trump is back at the table.

Settle in folks, this one could go long. There are two reds up at the baulk end, and the rest are still in the pack.

But Judd Trump, perhaps knowing he has to take risks, goes for an extravagant double on a red. It doesn't come off, and Williams sinks the long pot. Could he be away now?

Lee Walker - Mark Williams' coach and former World Seniors champion - has been speaking to BBC Two:

"The standard in the past two sessions has been unbelievable. Fingers crossed, Mark can get over the line.

"His long-potting for the tournament is 65% and in practice, if you're getting seven out of 10 that's really good, so to do it out there is incredible.

"If he can get through the first round [of a tournament] he is always dangerous. Sometimes in the first round is when he can be vulnerable, but here he played a good first-round match against Wu Yize and the match against John Higgins could have gone either way.

"He's such a great competitor, so he's always got a chance."

The players are back, but for how long?

Judd Trump breaks in the 29th - and potentially final - frame of this match.

Image source, Getty Images

Fans were told they would not receive refunds for what was meant to be the fourth session of the semi-final between Ronnie O'Sullivan and Zhao Xintong.

Zhao's 17-7 victory over the 'Rocket' was delivered with a session to spare, meaning there will be no competitive action on Saturday afternoon at the Crucible.

An exhibition featuring Steve Davis and Dennis Taylor - 40 years on from Taylor's victory in their famous black-ball final - took place instead, along with a question-and-answer session with seven-time winner Stephen Hendry and 1997 champion Ken Doherty.

The World Snooker Tour (WST) said its box office terms and conditions mean it is "unable to offer ticket refunds or exchanges".

Ticket prices for the session, including fees, ranged from £121 to £660.

WST said: "This is the first time in over a decade that a semi-final has finished a session early, so it is a very rare occurrence and unfortunately beyond our control."

Image source, PA Media

Zhao Xintong began this season suspended from snooker after a match-fixing scandal but has been tipped by Ronnie O'Sullivan to be the sport's new "megastar" if he becomes the first Chinese player to win the World Championship.

Zhao, 28, lives just a 10-minute walk from the tournament's Crucible home in Sheffield. He is one match away from joining Terry Griffiths and Shaun Murphy as the only qualifiers to land snooker's biggest prize.

Should he triumph on Monday, he will be the only amateur ever to do so and the youngest winner since Murphy in 2005.

Read more about Zhao's return to snooker and his run to the final

Steve Sutcliffe
BBC Sport at the Crucible Theatre, Sheffield

Awaiting the winner of this match in the final of the World Championship is China's Zhao Xintong.

Last night he claimed a dominant 17-7 win over Ronnie O'Sullivan which ensured their semi-final came to an end a session early.

Leading 12-4, Zhao compiled breaks of 62 and 128 to dash any hopes O'Sullivan had of building some momentum after taking the first two frames of Friday evening's session.

While O'Sullivan, who is level on seven Crucible crowns in the modern era with Stephen Hendry, took the first frame after the mid-session interval, Zhao exhibited an incredible temperament to round off the match.

In front of a crowd overwhelmingly urging 49-year-old O'Sullivan to take the contest into Saturday, Zhao compiled breaks of 85, 63 and 88 to seal the most famous victory of his career.