Ken Doherty
1997 world champion on BBC Two

I think both players will relish the challenge here. When it gets to this stage of your career both players are going to really savour it.

There's some real important frames there for two legends of the game. Both tactical masters but whoever scores the biggest tonight will set themselves up for the final session.

Mark Williams takes the ninth frame with a break of 92 as he proceeds to clear the table. John Higgins' advantages is cut to just one frame.

Rob Walker
Commentator on BBC iPlayer

They have both got to stop the unforced errors. They are both really feeling it out there.

There's been 24 altogether so far.

Scrappy and dramatic.

Zhao Xintong looks set to go five frames clear but WAIT...

He fluffs an easy blue on the colours. THEN he goes in-off the blue. What a shocker!

Chris Wakelin pinches the frame and the deficit is three. He's had a lucky escape.

Image source, PA Media

John Higgins fails to capitalise and allows Mark Williams to sneak into the frame. The Welshman is able to work the pack and the black during a half-century break which edges him closer to reducing the deficit to just one frame.

Image source, Getty Images

Mark Williams gambles on cutting a red into the corner pocket. He misses and worse still the cue ball goes in off. Can John Higgins profit here?

It's great for snooker fans to see the longevity of the 'Class of '92' - John Higgins, Mark Williams and Ronnie O'Sullivan.

They boast a combined age of 148.

But where is the younger British talent? Thumbs up if you think the trio's enduring success is good for the game, down if not.

And let us know your views using #bbcsnooker, via WhatsApp on 03301231826 or text 81111 (UK only, standard message rates apply). Please leave your name on messages.

John Higgins nudges a red into the corner pocket with a long pot down the table, but there's very little on by way of colours. The Scot ambitiously attempts to cut the black into the middle pocket but to no avail. Higgins has a 7-6 lead in points during a tense start to the evening session.

Image source, BBC Sport/Getty Images

At a combined age of 99, two of snooker's all-time greats - John Higgins takes on Mark Williams - will continue their World Championship quarter-final this evening.

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?

BBC Sport takes a closer look....

Tentative safety play from both players to start so far as both John Higgins and Mark Williams try to settle themselves into the contest. Williams picks off a red at the top of the pack into the middle pocket, then converts the blue before a return to the cautious approach.

Steve Davis
Six-time world champion on BBC Two

We knew it was going to be hard-fought and that no player would run away with it. It's advantage John at the moment, just.

Right, here we go. John Higgins to break.

They've played 42 times and there's hardly anything to separate them, with John Higgins just ahead in wins against his old rival Mark Williams.

The players are just being introduced on to the stage at the Crucible. Mark Williams entering to the Tom Jones classic Delilah gets the biggest cheer of the walk-on tunes.

Kevin Boddy: The combined age of Mark Williams and John Higgins when their match finishes tomorrow will be 100 years and 22 days. When was the last time combined ages of players was over 100?

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 this evening and will be played to a finish on Wednesday from at 10:00 BST.

Steve Davis
Six-time world champion on BBC Two

What an amazing quarter-final line-up. There's something for everybody from the players in there and a storyline for whoever wins it from here.

There will be live coverage of this evening's matches on BBC Two from 19:00-20:00 BST then on BBC Four from 20:00.

You will be able to watch both games on BBC iPlayer and via the 'Watch & listen' tab above.

The four quarter-finals are, like the second-round matches, being played over three sessions and are the best of 25 frames.

They are taking place today and tomorrow. Here's where we are at:

• Tuesday evening session:
• Chris Wakelin 2-6 Zhao Xintong - Table One (9th to 16th frame)
• John Higgins 5-3 Mark Williams - Table Two (9th to 16th frame)
• Afternoon session (Resumes Wednesday morning):
• Ronnie O'Sullivan 6-2 Si Jiahui
• Judd Trump 5-3 Luca Brecel