Mark Allen won three of the final four frames to stay within one of Mark Selby in their scrappy World Championship semi-final.

Former champion Stephen Hendry accused the pair of casting a “dark cloud” over the Crucible with their attritional play during a second session on Friday that was halted three frames early.

Although it was hardly thrilling stuff, they at least managed eight frames in the opening session on Saturday, with Selby turning his 7-6 lead into an 11-10 advantage to set up a tense evening decider.

The morning belonged to Selby, with the four-time former champion opening up a 10-7 lead thanks to breaks of 63, 112 and 53.

But, despite the clear water, he still did not look comfortable and some loose play helped Allen pull back to 10-9, with Selby missing a blue in the 19th frame while attempting to force a re-spotted black.

He extended the gap to two in convincing fashion but it is Allen, bidding to reach his first World Championship final, who has a modicum of momentum after finishing the session with a break of 92.