Mark Allen takes commanding lead over Robbie Williams

Allen won the first three frames before Englishman Williams hit back with a break of 86.

The world number three won a mammoth fifth frame before stretching his advantage to 6-1. After his opponent won the next with a century, Allen made it 7-2 to leave himself three frames from victory. Allen and Williams will reconvene at 2.30pm on Wednesday.

Earlier in the day Jack Lisowski took a 5-4 lead against 2016 finalist Ding Junhui, while Kyren Wilson put one foot in the second round after storming into an 8-1 lead against Welshman Dominic Dale.

Meanwhile, three-time champion Mark Williams admitted he does not know whether he has played his last World Snooker Championship match after he suffered a dramatic 10-9 defeat to Si Jiahui in the first round.

Si continued his love affair with the Crucible as he followed up last year’s surprise run to the semi-finals by knocking out Williams in an epic clash.

Williams resumed with a 5-4 lead but it was the Chinese 21-year-old who hit the ground running on Tuesday, taking each of the opening four frames to go into the mid-session interval 8-5 in front.

Williams then won four of the next five to make it 9-9 and set up a decider, with Si holding his nerve to close out a narrow victory.

While Si will face Jak Jones in the second round, Williams confessed he did not know whether a return to the Crucible is on the cards but appeared to rule out immediate retirement.

When asked whether he will be back next year, Williams said: “Who knows? I’ll be 50 years of age next year.

“I looked around and loved every minute of it. Whether or not I’ll be back again, I don’t know.

“I’m not considering my future really, just it’s a tough game. You keep getting back to these venues and it’s hard.

“Most of the ones for a while now, you’ve just got to treat it as if you’re not going to get back here.

“I’m not retiring, just treating every one as your last one. Fingers crossed you’ll see me playing next year, who knows?”

Si made a lightning-quick start to the session, striking the ball with increasing authority as he reeled off four frames in a row with three breaks in the 60s.

Williams’ fightback began immediately after the mid-session interval as he reduced his arrears to 8-7.

Si bounced back to take the next frame with a nerveless display before Williams battled to victory in the next two to level the match and force a decider.

But Si reeled off a break of 77 to wrap up a memorable win.

He said: “The first half of the match was quite nip and tuck, neither of us had brilliant form.

“But later on he gave me a lot more chances to let me have that lead at 8-5. My opponent was really, really accurate towards the end so it went all the way to the deciding frame.

“I always thought ‘I am the challenger who’s trying to take him down’, so I didn’t really feel the pressure and that’s how I won it.”