At the age of 36 years and three months, O’Sullivan would become the oldest world champion since 45-year-old Ray Reardon triumphed aged 45 in 1978 should he triumph on Monday.

Matthew Stevens stands in his way of a first appearance in the final since 2008, when the game’s most thrilling player lifted the Crucible trophy for a third time.

However, Stevens recognised after finishing off fellow Welshman Ryan Day this morning that he would need to raise his performance at the semi-final stage, whoever his next opponent.

And if O’Sullivan produces the form he showed in afternoon and evening sessions today, the man from Carmarthen will surely be denied a third appearance in the final.

Robertson had little answer to O’Sullivan’s brilliance as the Chigwell showman won the opening six frames of the day to surge from 5-3 behind to 9-5 in front, aided by breaks of 44, 47, 97, 62 and 42.

He looked sure to make a century in the second frame of the afternoon but fell three points short, seeming to refuse the chance of a ton after failing to execute a kiss on a red quite as effectively as he wanted.

Rather than play a double, O’Sullivan nudged the white off the red and into the middle pocket.

Robertson would have known O’Sullivan was well capable of turning their match around, given the way the latter played in the middle session of his second-round match against Mark Williams.

But such knowledge was no use to the Melbourne-born 2010 world champion as he sat in his chair watching the heavy breaks pour in.

Robertson took the final two frames of the afternoon, the second with a morale-boosting break of 63, his previous highest of the session having been a mere 29.

The world number three began the evening session with purpose too, rattling in a break of 50 to narrow the gap to one frame.

If O’Sullivan was worried, he was giving nothing away.

Robertson gifted him an opening chance from a poor break and in went an immaculate 104, followed by 71 to establish a position of authority at 11-8.

Seeking a swift resolution, O’Sullivan sprinted to a round break of 100 before missing the yellow to close to one frame way from victory.

Robertson was not finished and made it 12-9 with a run to 89, perhaps seeking inspiration in Ali Carter’s fightback from the same deficit to beat Judd Trump in the second round.

And a 77 break from Robertson, who has set up home in Cambridge since joining the professional ranks nine years ago, briefly complicated O’Sullivan’s task.

Robertson’s hopes were soon snuffed out though, O’Sullivan rattling through another high-speed break, this time a 59, to make victory safe.