Snooker results: Ronnie O'Sullivan beats David Gilbert in Coral World Grand Prix

O'Sullivan hadn't been seen in action since the Scottish Open in December, having decided to swerve The Masters, and there were one or two signs of rust as he needed all seven frames to advance.

Still, Gilbert had luck on his side at times - not least when taking the second frame - and all of the momentum at 3-3, before O'Sullivan found a timely century to take the deciding frame.

A 126 total clearance made it six wins from six for O'Sullivan against Gilbert, and next he will face either Mark Allen or Liang Wenbo.

"I struggled, I was way off the pace," said 44-year-old O’Sullivan. "It was a strange game. He was much the better player and I was just hanging on.

"I had a couple of chances to win it at 3-2 but kept messing up positional play. I’ve had six weeks of playing on not-so-good tables so I have to get used to playing on decent tables again. My touch was all over the show.

"I was the underdog coming into the match as the lower seeded player. David’s had a much better season than me, the rankings never lie. It’s a scalp for me, I didn’t expect to win. I didn’t play as if I had nothing to lose, but I knew I was second favourite. A lot of people would have fancied David to beat me.

"I get a buzz when I play in front of anyone. I love playing, I enjoy hitting the ball, it’s the ultimate feeling. I’m loving the game, I’m here to enjoy the tournament and hopefully that continues."

It was O'Sullivan who started brightest, taking the first frame after the pair exchanged half-centuries, and it was evident that Gilbert was struggling a little to settle despite a sizeable contribution.

The Derby man then benefited from an outrageous fluke on the blue as he levelled the match, having missed the pot itself, and a precise long red at the start of the third frame suggested he'd suddenly turned a corner.

It didn't last, though, as O'Sullivan moved back in front thanks to a break of 53, and when Gilbert missed a red down the cushion in frame four it appeared the match was as good as over.

To his credit, Gilbert fought back to force a deciding frame with breaks of 69 and a fine 115, but a reckless and off-the-radar long red left O'Sullivan among the balls, and he made no mistake with a century of his own.

On the other table, Stephen Maguire let slip a 3-1 lead as Tom Ford rallied to win 4-3.

Maguire produced one of the comebacks of the season to beat Neil Robertson from 5-1 down at the Masters last month, but this time was on the receiving end as Ford moved into the last 16.

Despite making two centuries in the first three frames of the match and adding a break of 83 in frame six, Mark Selby was dumped out by Xiao Guodong who held his nerve brilliantly to win a tense deciding frame.

Selby raced out of the blocks with breaks 111 and 131 in the first and third frames but Xiao produced a century of his own in frame three, a run 101 maintaining the deliriously high standard, and when further contributions of 89 - a valiant attempt at a 147 maximum break - and 78 inched him in front at 3-2, an early shock was on the cards.

Still, this season's English Open and Scottish Open hero rallied to force a final-frame shootout but it was Xiao who prevailed, claiming a notable scalp to book his place in the second round.

Gary Wilson produced an accomplished display to beat Zhou Yuelong 4-1, breaks of 53, 58 and 51 doing much of the damage for last year's World Championship semi-finalist.