Mark Allen seals semi-final spot in the British Open after win over world number one Judd Trump

Allen posted the triumph, clinching victory with a break of 50 in frame eight, after Trump had threatened a fightback from 4-1 adrift.

The first frame proved to be a war of attrition as it lasted 49 minutes.

Allen looked like getting over the line but missed a red into the middle pocket which allowed Trump to get back into the frame. A lengthy safety battle on the yellow was won by Allen who slid in all the colours to move ahead.

A missed pot by Allen in frame two was punished by Trump as he compiled a break of 101 for the 1000th century of his professional career.

In frame three, Allen was in first but missed a cut-back into the bottom corner as Trump made a break of 62. After the world number one missed the final red to seal the frame, Antrim man Allen doubled the red into the pocket and completed the clearance on the colours to move ahead.

Allen’s lead would be extended to 3-1 at the interval as both players missed chances to get over the line. Ultimately, breaks of 42 and 36 helped Allen stretch his advantage.

Trump knew he needed a strong start to frame five and he was in first but another missed red proved costly as Allen accrued enough points to move 4-1 up and one away from victory.

However, Trump hit a break of 92 to reduce the arrears to 4-2 and then it looked certain to be 4-3 but the 35-year-old missed the green when well-positioned. Inexplicably, Allen would miss the yellow and Trump cleared up to move within a frame behind.

Allen was presented with a major chance to progress after Trump’s miss on the red and despite needing three bites at the cherry, a break 50 in frame eight sealed the win for the Northern Irishman.

Selby reached the semi-final after his third successive final frame decider victory this week as he edged out David Gilbert.