But when he made a miss in the seventh frame, the frustration spilled over into his body language as he flicked a middle finger in the ball’s direction.

O’Sullivan was warned about his behaviour by referee Colin Humphries, and has been told a repeat will result in him being docked a frame.

The 34-year-old is hardly a first-time offender though, having been in the dock with snooker officials frequently during his career.

In 1996 he was fined £30,000 after attacking a tournament official at the World Championship, and just four years ago he quit his UK Championship quarter-final against Stephen Hendry when only 4-1 behind in a first-to-nine match. In 2008 he was handed another financial penalty for making lewd comments during a press conference in China.

Today’s offence was not on the same scale as those however and O’Sullivan is unlikely to be worried by the warning.

The opening nine frames of the clash with Liang summed him up, with a touch of the good, the bad, and the ugly.

O’Sullivan developed a convincing lead to carry over into tomorrow’s concluding session, and should have little trouble converting that advantage into an opening victory.

Centuries in the third and fourth frames, an 86 in the eighth and a 56 in the ninth which could quite easily have become a 147 were the highlights from the title favourite’s perspective.

He will be less keen to revisit several other frames, however, during which he and the increasingly lax Liang traded blunders.

O’Sullivan has cast doubt on his ability to win again in Sheffield and add to the titles he won in 2001, 2004 and 2008, and it was difficult to draw too many conclusions from his first appearance.

The scoreline hints at near-total O’Sullivan dominance but it was 3-2 at one stage, and Liang will surely tomorrow reflect on the brown he missed in frame seven as a pivotal point of the match.

There was a long distance between the white and the object ball but it was a pot he would normally make.

Yet Liang played a poor shot, leaving both white and brown in mid-table for O’Sullivan who cleared up to pinch the frame on the black.

O’Sullivan’s centuries – 100 and 108 – were quickfire efforts, and he threatened a third of the afternoon in the eighth but broke down on 86.

And when he then fired in seven reds and blacks he had a great chance to finish the session with a maximum break – worth £157,000 in bonus prize-money. Nine 147s have been made at the Crucible and O’Sullivan has compiled three of them.

The balls could hardly have been any more conveniently placed and he clearly fancied it, yet he missed a routine red with the rest, and the chance was gone.

The 34-year-old grimaced, then knocked his cue against his forehead and retreated to his seat.

But he was soon up again as Liang missed an easy opener and O’Sullivan was back in with 39 to clinch his five-frame advantage.

The man O’Sullivan beat in the 2008 final, Ali Carter, made sure of his place in the second round.

The 30-year-old from Essex finished off highly-rated Jamie Cope 10-4.

“I’ve got no expectations, I’ve got no hopes of winning, I’m just playing snooker and seeing what happens,” said Carter.

Cope, 30, today fired in breaks of 75 and 83 as he converted a 7-2 overnight lead into his win.

Cope said: “I think I’m going to see a sports psychologist because I do think it’s the only problem stopping me challenging for titles.”

Former poker club croupier Martin Gould provided the first shock of the tournament as world number eight Marco Fu folded against him.

Qualifier Gould, the 28-year-old from London, inflicted the latest in a string of painful defeats for Hong Kong’s Fu this season.

He won 10-9, firing a break of 90 in the decider, after Fu allowed an 8-6 lead to slide away.

Gould is guaranteed £16,000 and said: “It’s my biggest pay day so far but money doesn’t really bother me.”

China Open champion Mark Williams tonight clinched his place in the last 16, as the Welshman beat Scotland’s Marcus Campbell 10-5.

Williams, world champion in 2000 and 2003, was struggling for form in the morning session but stepped up his performance after they resumed and pulled away to earn a comfortable win.

O’Sullivan is Williams’ likely next opponent.

“Hopefully it’ll be as good a match as it looks on paper,” said Williams.

Williams revealed he has been having problems away from snooker, saying: “I haven’t sorted them all out yet but I’m getting there.

“You’ve got to be good off the table to be good on the table. I’m having a few problems at the minute.”