So, we'll have live coverage of Ronnie O'Sullivan v Si Jiahui on BBC Two while the other quarter-final between Judd Trump and Luca Brecel will be available to watch via BBC iPlayer.

You can, of course, watch both matches by clicking the 'Watch & listen' tab above.

Dennis Taylor
1985 world champion on BBC Two

To be honest I never take a lot of notice of what Ronnie says about how he's playing because it's often not a reflection of how he is out on the table. He's only lost eight frames so is in pretty good form. The new cue is giving him a few issues but only on long shots when he has to play with a bit of side. His break building is as good as it has been.

The balls are racked on both the tables. The players are just lingering behind the scenes ready for their entrances to the playing area at the Crucible Threate.

Four-time world champion John Higgins took advantage of some mistakes from Mark Williams to lead 5-3 after the first session of their World Championship quarter-final.

In the other match, China's Zhao Xintong took control of his quarter-final tie with Chris Wakelin and is currently 6-2 up on the Englishman.

You can read more details in Michael Emons' report from the Crucible...

Both of those matches will resume at 19:00 BST this evening.

Steve Davis
Six-time world champion on BBC Two

We hear what Ronnie says about the confidence levels but he doesn't play by the same rules as everyone. Among the players we don't take much notice of that because he is so good.

How he feels is another story and I'm sure he's being candid and honest when he says it - I am sure of that. I don't think it's trying to deflect or play it down.

Image source, Getty Images

Ronnie O'Sullivan expects his quarter-final with Si Jiahui to be the "acid test" for the seven-time world champion's comeback after a three-month hiatus from the game.

The 'Rocket' comfortably negotiated an opening-round clash with old foe Ali Carter before putting Pang Junxu to the sword 13-4 in the second round.

But O'Sullivan expects 2023 semi-finalist to be more ruthless than both of his previous opponents.

"This will be the acid test because he does score," O'Sullivan told BBC Two.

"The opponents I've played in the first two rounds have had enough chances to put me away but they haven't.

"I think this guy will - he beat me in Saudi Arabia this year, I was scrapping but his scoring power was just too much for me.

"Three-session game, best of 25, I'm going to have to see where I'm at."

Steve Davis
Six-time world champion on BBC Two

We've heard Ronnie O'Sullivan say things before about where his game is at and then he's produced some fantastic snooker. I still don't think he's tuned into the new cue he has got, but the longer he is in the event the more he will tune into it.

It's fair to say neither Ronnie O'Sullivan nor Si Jiahui have been overly enamoured with their performances so far at the Crucible - yet one of them will reach the semi-finals.

O'Sullivan puts his progress down to adversaries playing badly while Si said his scrappy 13-10 second-round win over Ben Woollaston was the worst he'd ever played at the Sheffield venue.

The 'Rocket', however, made 12 breaks over 50 in thrashing Pang Junxu 13-4 in round two - and has made six centuries in his two matches so far.

He's looking, of course, to make the Crucible title record his own with an eighth crown - level with Stephen Hendry on seven - while Si bids to make the semi-finals for the second time and go one better than his unforgettable collapse to Luca Brecel in 2023.

Image source, Rex Features

Shaun Murphy
2005 world champion on BBC Two

For Judd Trump it's all about sustaining that incredible level he has hit so far. If he stays at the level he is playing today he will win the World Championship again. If he doesn't stay at that level it will be a fairer fight. There's nobody across all aspects of the game doing what Judd Trump is doing right now.

Image source, Rex Features

Arguably two of the tournament's form players meet in a last-eight tie that will have lovers of 'naughty snooker' salivating.

Belgium's Luca Brecel and Bristol's Judd Trump are among the game's great entertainers - but only have one World Championship title apiece.

For Trump, in particular, that's a baffling stat but, having shown grit as well as glamour in beating Shaun Murphy, it's one he appears determined to change.

Brecel was dazzling in thrashing Ding Junhui in round two and, after two years when he's often gone missing, appears back to the form that took him to this title in 2023.

We're back...

Hopefully you are all suitably nourished after lunch and ready for some drama from the Crucible Theatre. We've got a couple of cracking matches coming your way.

That's it for the live text updates for now, but we will be back from around 14:15 BST to build-up to this afternoon's crackerjack action.

Meanwhile you can follow BBC Two coverage or click on the link at the top of this page.

Afternoon session from 14:30 BST:

• Ronnie O'Sullivan v Si Jiahui - Table One (1st to 8th frame)
• Judd Trump v Luca Brecel - Table Two (1st to 8th frame)

Image source, BBC Sport

Chris Wakelin has been battling to stay in his quarter-final against Zhao Xintong and having won the first frame he's able to salvage something by banking the last of the session.

Zhao made him work, though, and only a marginal blunder from the Chinese player to a Wakelin safety shot on the green opened the door for the Englishman.

Wakelin kept his cool cutting in the green, and then managed to pot the remaining colours - save for the black - to get another one on the board but he's still got a four-frame deficit to overcome.

Michael Emons
BBC Sport at the Crucible Theatre

Four-time world champion John Higgins took advantage of some mistakes from Mark Williams to move into a 5-3 lead after the first session of their World Championship quarter-final.

This tie features two of the sport's all-time greats and two thirds of snooker's legendary 'Class of 92' trio, which also includes Ronnie O'Sullivan.

Williams, 50, became the oldest man to reach the last eight at the Crucible since Steve Davis did so at the age of 52 in 2010, while Higgins turns 50 on 18 May, 13 days after this tournament's final.

Both men received a fantastic standing ovation when introduced to the crowd, with the spectators then treated to some high-quality snooker.

A break of 69 took Higgins ahead, but Williams should have levelled only for the Scot to snatch the frame on the black following a run of 65.

An effort of 72 gave the Welshman his first frame, only for him to miss a brown in the fourth frame and that proved costly as Higgins took the first of three frames in a row.

Being 5-1 ahead, Higgins would have hoped to have stretched his lead further, but Williams responded well with breaks of 104 and 59.

The best-of-25 match resumes at 19:00 BST and will be played to a finish on Wednesday from at 10:00 BST.

That's a good response from Mark Williams, who has made the first century of the match with an effort of 104 to claw one back. He trails 5-2 with one frame to go in the session.

That's three frames in a row for John Higgins, who has now jumped into a 5-1 lead to ensure he will hold the advantage going into the second session, which starts at 19:00 BST.

The Scot has just made the highest break of the match so far with 80 in the sixth frame.

Two more frames to go. Williams will be aiming to win them both and being 5-3 behind would look a lot better than 6-2 or 7-1.

Michael Emons
BBC Sport at the Crucible Theatre

Image source, PA Media

Players from eight countries have won snooker's most prestigious title and become a world champion - but China is still waiting for its first success.

But could 2025 be the year that changes? Two of the eight quarter-finalists are from China, Zhao Xintong and Si Jiahui, with Zhao holding an early lead in his last-eight tie with Chris Wakelin.

So what happens to snooker if a Chinese player lifts the famous trophy on Monday, 5 May?

"It's something the authorities we've been working in China with have dreamed of, that one day they would have the world champion," said WPBSA chairman Jason Ferguson.

"If a Chinese player wins it would be magical, a historical moment, a real shift in the sport, and I can't tell you the media frenzy it would cause for snooker around the world."

"There's no doubt that player would become a national hero."

• Read more on our feature on the growth of snooker in China.

Both John Higgins and Zhao Xintong have moved into three-frame leads with the scoreboards showing it as 4-1 in their matches against Mark Williams and Chris Wakelin respectively.

That means Higgins and Zhao cannot be trailing going into the second sessions. Three frames left on each table today.

Michael Emons
BBC Sport at the Crucible Theatre

Image source, Getty Images

At a combined age of 99, two of snooker's all-time greats go head-to-head on Tuesday as John Higgins takes on Mark Williams with a place in the World Championship semi-finals up for grabs.

The sport's legendary 'Class of 92', with Ronnie O'Sullivan completing the trio, have won 14 world titles between them - and are all still going strong this year.

Williams turned 50 last month, Higgins reaches his half century 13 days after this year's final with O'Sullivan celebrating his 50th birthday in December.

But they have proved that age is just a number.

Could one of them again go all the way at the Crucible?

• Read more of our feature on the 'Class of 92' on the BBC Snooker index.

BBC Radio 5 Live

Lee Walker, Mark Williams' coach, spoke to BBC Radio 5 Live Breakfast earlier today and was understandably excited for this match.

"This is two legends of the game going head to head," said Walker. "I wouldn't really say Mark has got the edge - it's just two of the greatest players there's ever been.

"When they were playing years ago, they were great rivals but now they've got great respect for each other and I think for both of them, they're really looking forward to playing against each other.

"Mark's 50. John's 50 in a couple of weeks time. They're not going to be around forever - this could possibly be the last time they play each other at The Crucible. This could be a match that you go on to make the most of and I'm hoping it'll be an absolute cracker.

"If this is half as good [as the 2018 final when Williams beat Higgins 18-16], then everyone's going to be in for a treat today and tomorrow."

• Have a listen to the interview from BBC Radio 5 Live Breakfast