Steve Sutcliffe
BBC Sport at the Crucible Theatre, Sheffield

Wow. John Higgins was labouring early this morning but now we are getting the thriller that was promised on Tuesday.

There are one or two fortunate journalists in the press room off to watch this final-frame decider from the second commentary box which is now free, just to listen to the reception these two legends of the game get.

Higgins has not lost a Crucible decider since 1996.

This is going to be a match that is talked about for years to come. Williams was 5-1 down, then 12-8 ahead.

Higgins has now forced it into a decider. Brilliant drama.

A one-frame shootout for a place in the World Championship semi-finals.

Image source, PA

Ken Doherty said this would be the "tie of the round" and he's been proved absolutely spot on.

John Higgins looked finished at the mid-session interval, trailing 12-8 with Williams one frame away.

Higgins has been sensational since with breaks of 93, 114 and now 67.

But, with hampered cueing, he misses a red. Williams come to the table 67 behind, with 67 on.

We could be heading for a respotted black, but the table is not inviting. Any Williams error and we're going to a decider.

Higgins in again at the start of frame 24 of 25. He got a bit fortunate to pot a red right at the beginning but has control of the table, 21 and still going.

Is he going to force the match into a decider? Brilliant entertainment.

Mark Williams is cueing over the blue when using the rest to pot a red, but then commits a foul as he has nudged that blue.

And it is punished to the maximum as Higgins then rattles in a superb century break of 114 for the 1,039th century break of his career.

What a competitor. That's breaks of 93 and 114 in two frames after the mid-session interval.

A maximum of two frames left in this brilliant match. Williams needs one of them, Higgins needs both.

It's becoming an epic, just as we hoped it would

Mark Williams remains one frame away from victory, while John Higgins closes to two after a superb break of 93 in frame 22.

Si Jiahui loses position on 28 and misses the brown. His cue ball was all over the place there.

He gets another chance mind but can't drain a long red to the left corner. And he must know what is coming know....

Ronnie O'Sullivan makes no mistakes to take the final session of the morning with a run of 64. He has a healthy lead going into this evening's concluding session.

John Higgins keeps the match alive by winning the first frame after the restart, and comes to the table 15-0 behind but with the table open in the 22nd frame.

Si Jiahui is playing his way back into this match.

He gets to 52, but goes in off into the right middle when potting the green.

However, he is quickly back at the table and is able to close the gap to just three frames.

Higgins does get back to the table, but he has no room for error. Any mistake now and he could well be out of the tournament.

Higgins gets to 49, and was perfect but any maximum thoughts are soon ended with a miss on the black off the spot. Again Williams handed a chance. Has Higgins just played his last shot at this tournament?

It must feel like what could have been for Si Jiahui.

A break of 61 helps him get a fifth frame on the board but it really should be his sixth.

Steve Sutcliffe
BBC Sport at the Crucible Theatre, Sheffield

An absolute hammer blow!

Si Jiahui looked poised to reduce his arrears to 8-5 but ends up 9-4 down.

He was 43 ahead with 43 on the table when he missed the penultimate red to the left middle and he then finds himself snooker on the final red before going on to lose the frame.

Ruthless from 'The Rocket'.

It has been a great first four frames for Mark Williams as he has won them all to move one frame away from the semi-final.

There will be a lot on John Higgins' mind at the mid-session interval as he had chances to win all four frames but either missed or ran out of position having scored 40 in frame one, 21 in frame two, 27 in frame three and 18 in frame four.

This is the last frame before the mid-session interval and you really feel John Higgins needs to get it.

If it goes Mark Williams' way, he will only need one more frame when they resume. It's currently 19-0 to Higgins with Williams at the table.

They have played three frames today, Mark Williams has won all three, but John Higgins has had chances in all of them.

That miss on the blue costs Higgins the 19th frame and Williams now only needs two more for the victory.

Remember, he was 5-1 down yesterday so what a recovery it would be.

Just as I say that, Higgins misses a blue on the spot into the right middle. "You can't be missing those," says John Virgo on TV commentary.

Williams made 53 after the Higgins miss, but then had to play safe. After a few shots, he leaves a red peeking out and Higgins downs it with a lovely long shot. A chance for the Scot to get on the board today.

A shake of the head, a look of frustration from John Higgins. For the third frame in a row, he falters early on and gives his opponent a massive chance

Higgins has now missed after scoring 40 in the first frame of the day, 21 in the second frame and now 27 in the third.

Williams has ruthlessly punished those first two errors, can he do the same here again?

You can almost sense the relief as Si Jiahui clinches the 12th frame, although he gave Ronnie O'Sullivan the chance of a counter after breaking down on 52.

With that frame in the bag for Si it means the match is guaranteed to go to a third and final session this evening at 19:00 BST.