Mark Selby admitted he doubted whether he would ever return to the one-table set-up at the Crucible after completing a 12-7 win over Neil Robertson to book his place in the World Championship semi-finals for the sixth time.

Selby suffered a crisis of confidence in the wake of his third world title win in 2017, losing his world number one ranking as he won just two tournaments in the following two years and crashed out in the early stages in Sheffield.

But the 37-year-old, who was forced to battle through the first two rounds against Jordan Brown and Noppon Saengkham respectively, believes the manner of his win over fellow former champion Robertson indicates he is back to somewhere approaching his best.

Selby said: "Over the last 12 to 18 months I was questioning myself. I had got so used to winning tournaments than when I wasn't winning tournaments it became very damaging to my confidence.

"I was happy with my performance against Neil. I felt if I got a chance I could score, and my safety play was back up with how it was a few years ago.

"As a match-play game it was right up there with my best performances. I can see the changes already, especially in my body language, so long may it continue."

Selby resumed with an 11-5 overnight advantage and swiftly moved one frame away from victory by taking his first chance with a break of 91.

Selby moved to the verge of victory with a 56 break in the next frame but after missing a red to the middle, Robertson embarked on a gutsy comeback.

The Australian chiselled out the next two frames and looked set to take a third before a simple missed black allowed Selby in to wrap up victory at the second attempt.

Robertson said: "It was a really tough game and apart from three or four frames in the match, every frame came down to the final few reds or the colours.

"Mark's defensive safety was absolutely unbelievable. He didn't let up really and I think he got his game plan spot-on over over the two days.

"He kept it super-tight and I couldn't get any free-flowing scoring going at all." 

Elsewhere at the Crucible, Anthony McGill held off a fine fightback from Kurt Maflin and will take a 10-6 lead into Tuesday evening's concluding session of their quarter-final.

The Scot extended a 7-1 overnight advantage to 9-3 before Maflin won three frames in succession, culminating in a fluked pink to give him hope of mounting a comeback.

However McGill held his nerve to take the last frame of the morning session at the second attempt and requires three further frames to book his first semi-final slot.