Williams admitted he had no answer to his opponent, tweeting from his dressing room: “That was tough – I’ve not got enough cue power to combat tough conditions like Zhao. His cue power is superb. Prob the best potter I’ve ever seen.”

Neither player was at their best in a tetchy session in which Williams scrambled to avoid becoming the first player since Jimmy White in 1993 to lose a Crucible final with a session to spare.

He achieved it with a break of 66 in the 23rd frame only for Zhao to restore his advantage with a 67, the highest break of the session, before he capitalised on a missed red from Williams in the last with a clearance that moved him to the verge of victory.

If and when Zhao completes the job later on Monday he will become only the third qualifier to win the title after Shaun Murphy and Terry Griffiths, as well as the first amateur, having lost his tour card as a consequence of his 20-month ban for his involvement in a betting scandal in 2023.

Zhao resumed his comeback on the Q Tour last September and won 46 of his 48 subsequent matches to reach the Crucible final, including sweeping through four qualifying rounds, a record for a prospective winner.

Williams, at 50 the oldest Crucible finalist, needed a fast start to have any hope of making a fight of the final session, but a missed blue to the middle handed his opponent the chance to extend his lead to 12-6.

Williams did win the next despite jawing a pink to the middle, before Zhao won the next two to give himself a shot at wrapping up an early win.

Williams avoided that embarrassment by winning the next but blew his chance of clawing a little closer, and with that turned the prospect of a pressure-filled final session into a virtual coronation for his unflappable 28-year-old opponent.