A bizarre blunder from Mark Allen nearly left TNT Sports commentator Philip Studd speechless at the World Snooker Championship. The incident took place during the early stages of the 19th frame in the semi-final between the Northern Irishman and Wu Yize. Allen was losing 10-8 and needed a solid start to halve the deficit and stop his Chinese rival from pulling away.

With the cue ball near the top of the table and the pack of reds slightly open, Allen was looking for a safety shot to put Wu in a difficult position. His path to the gaggle of reds was slightly obscured by the brown, but there was still an open line. The shot looked easy enough for a player of Allen's calibre, but an unusual mistake saw him clip the brown on the way down the table.

It prompted a gasp of surprise in the commentary booth as Allen simply stared ahead before walking back to his chair.

Studd was astounded and said: "My goodness. What has he done there? I think if the red goes past the blue into the yellow pocket he'll play it, but... wow, certainly [referee] Marcel Eckhart wouldn't want to be replacing balls here if he didn't have to."

Fortunately for Allen, he quickly regained his composure to win the frame with a break of 85. He followed up with another triumph to level the scores at 10-10, with very little to separate the two players.

Ken Doherty, who secured Crucible glory in 1997, said on BBC Two: "It's turning into an absolute cracking semi-final.

"The players are in great form, great safety play, and when they're getting in they're making some wonderful breaks. Shame there's no century, but it's a wonderful break."

It came a day after Allen and Wu played out the longest frame in World Snooker Championship history, clocking in at just over 100 minutes.

No balls were potted for nearly an hour with the two players locked in a tedious battle of attrition. Allen led the frame 47-13 and so did not want a re-rack and the crowd began to show signs of frustration, with slow clapping breaking out at one point.

Eckhardt eventually took control of the game after a word from a higher-up, explaining to both Allen and Wu that they had just three shots to change things or face a re-rack.

The deadlock was eventually broken when Allen fouled by knocking in the black, allowing Wu to move ahead and win the frame.

Six-time Crucible king Steve Davis wasn't happy and said: "In a nutshell, that frame's an embarrassment to snooker, and the referees' and the players' association need to try and work out a way that never happens again."

Fellow champion Kyren Wilson added: "Marcel should have called that a lot earlier. That frame was going nowhere. Quite painful."

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