Ronnie O'Sullivan knocks in a lovely long red but can't develop a colour so plays safe. An early test for Si as they duel from baulk.

Steve Sutcliffe
BBC Sport at the Crucible Theatre, Sheffield

There are some familiar faces in the media room this evening and all the chat is about potential semi-final storylines.

Will Ronnie O'Sullivan end up facing Zhao Xintong? And just how do you predict a winner from Luca Brecel v Judd Trump based on what we've seen so far?

Ronnie breaks off in frame 17.

Rob Walker
MC at the Crucible

The greatest player in history is just three frames away from a 14th semi-final. Blink and you'll miss him, the rocket Ronnie O'Sullivan!

This is some session to have a ticket for. Two cracking matches coming to a conclusion and the place is fizzing.

Rob Walker
MC at the Crucible

A place in the semi-finals is a massive prize in our sport.

What a run it has been from Luca Brecel, he is back to his swashbuckling best. And here comes the most prolific man of his generation, the current world number one, the ace in the pack, Judd Trump!

Stephen Hendry
Seven-time world champion on BBC Two

It's the last session of the quarter-final, you've got to stop yourself from thinking ahead to the one-table situation.

Mark Williams is my hero, he really is. What he is done at the age of 50 is amazing - and he can't see!

Luca Brecel is one on tonight and he's going to take some stopping.

Steve Sutcliffe
BBC Sport at the Crucible Theatre, Sheffield

Three-time winner Mark Williams held off a spirited John Higgins fightback to win a Crucible classic 13-12 on the black as he reached the semi-finals.

Resuming at 8-8 on Wednesday, Higgins was initially left to rue costly misses in each of the first four frames as winner Williams reeled off all four with three half-centuries along the way.

Williams, 50, who had trailed 5-1, took the 20th frame but was then largely confined to his chair as four-time champion Higgins delivered a stirring response from 12-8 down.

The 49-year-old, who appeared to be labouring, suddenly found his rhythm and compiled breaks of 94, 114 and 67 to set up a dramatic finale.

Both players had opportunities to clinch a tense final frame but when Higgins rattled the jaws of the corner pocket on the blue, the Welshman capitalised to become the oldest player to reach the last four since 52-year-old Ray Reardon in 1985.

"Unbelievable game, unbelievable finish. The blue I played was probably one of my best shots for many years," Williams told BBC Sport.

Luke Guest: This is scary snooker from Brecel and Trump, can’t see anybody stopping the winner of this one

Image source, PA Media

Who's your favourite, where are you following from, how good has the tournament been - whatever you want to get off your chest, here's the place to do it.

Just make sure your names are on any messages, please.

These two warriors have only had about 90 minutes off the table between sessions. Barely time for a brew and a quick tea.

Wonder what was on the menu?

Image source, Reuters

And on table two, an absolutely brilliant match between two former champs.

Both players played some incredible stuff this afternoon to leave the audience on the edge of their seats.

This one could go DEEP.

Image source, Reuters

On table one tonight Ronnie O'Sullivan is looking for the three frames he needs to motor into his 14th World Championship semi final.

In his way, 22-year-old Si Jiahui from China who moved to Sheffield at the age of 16. They both know their way around these tables that's for sure...

Image source, Getty Images

It's been another scintillating day in Sheffield.

While Britain blazes in the heat, the Crucible has been cooking too.

And don't expect things to cool off between now and closing time...

Image source, Reuters

We've had plenty of drama already today and we're going to pause our live text updates for now.

We'll be back for the evening session at 19:00 BST. And it promises to be a cracker as the final semi-finalists will be confirmed.

You can continue to watch BBC Two coverage until 18:00 - there's a link at the top of this page.

Evening session from 19:00 BST:

• Ronnie O'Sullivan 10-6 Si Jiahui - Table One
• Judd Trump 8-8 Luca Brecel - Table Two

Dennis Taylor
1985 world champion on BBC Two

What a session of snooker we have witnessed here this afternoon.

Brecel can't get the snookers and, with the match set to resume at 19:00 BST, says that's enough. He wins the session 5-3, that makes it 8-8.

It is the best-of-nine tonight for a place in the semi-final.

Brecel misses with a swerve shot, fouling and that helps Trump get more points. Brecel plays on despite needing two snookers.

Trump holds a 52-25 lead, but Brecel pots a fortunate red with the rest. But he then loses position going to the final red and Trump gets another opportunity, 52-31.

Brecel blasts away a red and then a blue, but then goes in-off and Trump has another chance to save the frame, but trails 13-25.