Allen’s clearance came in the seventh frame of his second round match against Rod Lawler, putting him 4-3 up. After leaving the arena to compose himself, he then won the next two frames to complete a 6-4 victory.
Allen, a beaten finalist at the Barbican five years ago, came close to a 147 in 2010 at the World Championship, potting 15 reds and 15 blacks before missing the green. He then went on to make a 146 in the same competition.
He told the BBC: “It was a big buzz because I’d never made one on tour. The balls were sitting so nice from 24 and I was thinking about it from then. The reds were all sitting, none on the cushions, and you can only mess it up from there.
“I’m very very happy to do it. It was relief when the black went in. I was nervous and I was shaking. I was thinking ‘just please pot it’ because if you miss now you look silly’.
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“I went to the toilet afterwards to calm myself down and take deep breaths, control the breathing and take the shakes away. Then I was ready to start the next frame and ready to win the match because you know your opponent is going to make it tough, no matter how well you’re playing.”
Allen felt the scoreline flattered his opponent a little and felt his margin of victory should have been wider.
“It was a weird match because I felt I played much much better than 6-4,” he said. “Rod won a couple of very close frames when he had a better run of the balls. I honestly could’ve won 6-1 or 6-2 the way I played but he just hangs on and hangs on.
“I’m feeling my game is in good shape and I’m confident and confidence is massive in our game.”
Earlier in the day, five-time champion Ronnie O’Sullivan cruised into the third round with a 6-0 win over Rhys Clark.
The young Scot’s nerves got the better of him in the opening frame and O’Sullivan capitalised in ruthless fashion, taking a 4-0 interval lead with breaks of 112, 79 and 82.