One relevant difference between the pair is that Campbell has played a full season on tour, while O’Sullivan is returning from almost a year out of the game.

And while he has stressed practice is going to plan, O’Sullivan has been aware that taking on even a relative journeyman such as Campbell cannot be considered a formality.

The four-time champion said: “They’re all tough players. I played him last year in Beijing and was 4-2 down and managed to scrape over the line 5-4.

“I’ve known Marcus for years, he’s a great match player. Most people who come from Scotland are great match players, it’s just the way they’re built.

“He’s been grinding away all season. I’m in a tournament I didn’t expect to be playing in so it’s an adventure.”

O’Sullivan and Campbell were getting under way at 10am, and finishing this evening.

Theirs was the only match due to conclude today, with two-time former champion Mark Williams, 2005 winner Shaun Murphy and rising star Jack Lisowski among the players beginning their matches.

O’Sullivan has admitted he found it difficult to switch off from snooker after announcing his hiatus from the sport in November.

“Once I finished, I did watch a couple of events, and I thought, ’I’ve sat all day watching snooker’. Then I just got on with my life and I didn’t watch anything after the UK Championship,” he said.

“At one stage I thought I might be watching snooker until I was about 80 sitting in my armchair, but once you’re out of something you find other interests.”

There was not enough to keep O’Sullivan away from the baize though.

World Snooker chairman Barry Hearn is delighted to see O’Sullivan back among his flock.

“The return of Ronnie has added another dimension, no question,” Hearn said.

“I hate sport that’s already written out and you know what’s going to happen.

“I have no idea what’s going to happen and I have absolutely no idea which Ronnie O’Sullivan’s going to turn up.

“You always need heroes and villains in any good soap opera. I’m not saying Ronnie’s either, but he’s certainly capable of being both.”

World number one Mark Selby is in awe of O’Sullivan’s inert ability, saying: “He’s more than capable of turning up and winning the World Championship.

“I’m one of those players where I need to be practising all the while to keep sharp, because if I put my cue down for a few months and go down to the club it’s more or less like starting again.”