Barry Hawkins adds 46 to his score before a tough long red to the green pocket stays up.

Back at the table, Mark Allen tries to develop one of the two remaining safe reds but can't do so.

Allen trails by five.

Steve Sutcliffe
BBC Sport at the Crucible Theatre

Image source, PA Media

MC Rob Walker aptly described last night's session between Barry Hawkins and Mark Allen as "snooker from the gods" but this morning's opening frame was very much more gritty match-play stuff.

And at present Northern Ireland's Allen, 40, is delivering on both fronts. Could this be the year he ends his long wait to triumph at the Crucible?

The World Championship trophy has eluded Allen so far and he has reached just two semi-finals in 19 previous attempts.

However, if he was to be victorious this time around he would become the oldest first-time winner in the modern era, eclipsing Stuart Bingham, who claimed the world title in 2015, aged 38 years and 343 days.

Neil Robertson clears the remaining balls for a break of 48 to go three frames in front of fellow former world champion John Higgins.

Mark Allen makes the first break of the 18th frame but it ends on 35 with a missed red - in his defence, it was awkward cueing over other balls.

What can Barry Hawkins do in reply?

Approaching the 40-minute mark in the opening frame of the morning session between Neil Robertson and John Higgins.

It's a frame that has followed the same pattern as much of yesterday's first session, with passages of safety play and the occasional chance, but neither player able to make a frame-winning contribution.

Robertson drills in a long red and, narrowly ahead, has an opportunity to clinch it now.

This is the draw bracket for the final stages of the World Championship.

The top section contains the four former world champions in the draw, while the bottom half is filled with players aiming to win the event for the first time.

Mark Allen pots the pink to clinch the 17th frame and move within four frames of victory.

It's the first time he's led in this match since he was 2-1 up on Tuesday morning.

Barry Hawkins has potted the green and brown, meaning he only needs one five-point foul from Mark Allen on the blue to give him the chance to tie.

Allen, having escaped one snooker, missed a pot on the blue so this frame continues.

Robertson leads 36-32 in the opening frame of the session against John Higgins, with five reds remaining on the table.

Image source, PA Media

Barry Hawkins hit a red with his second attempt to escape the snooker, but left Mark Allen with an easy starter.

Allen clears up to the yellow to leave Hawkins needing two snookers - and the Englishman elects to play on.

Mark Allen's break ends with the man from Northern Ireland seven points ahead.

The three remaining reds are all at the baulk end but in the open, so whoever pots the next ball will be a strong favourite.

Allen helps his cause by snookering Barry Hawkins behind the black.

A safety exchange comes to an end when Neil Robertson, 36 points up, goes for a long pot and misses, leaving John Higgins in among the reds with a chance to score.

There's a scheduled eight frames to be played in the second session of this match, with a possible nine in the final session from 19:00 BST.

Four reds left now and Mark Allen, on a break of 37, is into the lead in frame 17.

Barry Hawkins is back at the table with another chance to clinch the opening frame of the morning.

The blue and black are in the open and there are plenty of reds to go at...

But a mid-distance red wobbles in the jaws and stays up.

Hawkins leads by 35 but Mark Allen has a real opportunity to reduce that advantage now.

A quarter-final of supreme quality comes to its conclusion this morning - these were the match stats before the start of the final session.

The pot success percentages and highest break figures below say it all.

Neither player deserves to lose - but one of them has to.

Lee Walker
Former World Seniors champion on BBC Two

When you get to this stage, both players have won a couple of matches, both are in the groove and you can get some incredible matches.

This has certainly been one.

Image source, PA Media

Barry Hawkins knocks in a long red to earn the first chance of the morning against Mark Allen.

With the break up to 15, he pots the black and goes into the pack, but the split isn't the best and he's left with a tricky cut-back into the corner, which stays in the jaws.

Neil Robertson's record at the Crucible is not quite what you'd expect for a player of his undoubted quality.

The Australian has only appeared in one final during his career - when he won the world title in 2010 - and has not got to the semi-finals since 2014.

He's just started with a sensational long, straight red - hopefully a sign that the second session of this match will be a bit more open than the first.

BBC Two

MC Rob Walker has introduced the four players to the Crucible crowd, so we are not far away from the first live snooker of the day.

You can watch every shot of the World Championship live on the BBC.

Both of this morning's matches are live via the "Watch and listen" tab on this page and available on the BBC iPlayer.

There's also live snooker on BBC Two until 11:15 BST - focusing on Barry Hawkins v Mark Allen - and plenty more on that channel later in the day.

Ken Doherty
1997 world champion on BBC Two

The standard and barrage of breaks in that session was incredible. Both players are on top form and it's going to be an exciting finish.