Defending champion Ronnie O'Sullivan clicked into gear to take control of his box-office Betfair World Championship semi-final with Judd Trump.

The game's two great entertainers were locked at 4-4 overnight and 6-6 at the mid-session interval this morning, but the more experienced O'Sullivan reeled off three frames in a row to take a 9-7 lead in the race to 17 heading into tonight's third session.

The Essex potter had the chance to make it a mini clean sweep after the break but missed a routine green to let Trump in for a frame he deserved based on the amount of misfortune he suffered throughout the morning.

But, although he came back from five frames down to beat Shaun Murphy in an epic quarter-final, the odds are stacked against Trump making a second final in three years, with O'Sullivan, by his own admission in his swansong tournament, looking up for the challenge.

While the 37-year-old has caused a storm by saying he is only defending his title in order to pocket the cash and pay his children's school fees, his performance told a different story - one of a man desperate to retain his title.

His safety play was of the highest order and he won two frames thanks to the quality of it, while his point-scoring was heavy enough after he shook off some early rustiness.

It had been suggested in the wake of his comments about his motives for playing that O'Sullivan would lose some of the vociferous support he has always been able to count upon, but there was no evidence of that today.

One fan was particularly vocal when Trump undercut a pink on 27 in the opener, shouting out that O'Sullivan should "show him" - perhaps in reference to Trump saying on Wednesday that his opponent did not scare him. O'Sullivan answered the request with a clearing 90.

Trump was not looking particularly nimble among the balls and let out an audible groan when he fluffed a red on 35, but an identical contribution got him over the line and level again.

A fascinating 11th frame fell on the side of O'Sullivan thanks to a brilliant behind-the-yellow safety. He clipped a top-cushion red to get Trump in all sorts of trouble and knocked in a timely 34 to the pink.

Trump was as good as his word in not being intimidated, though, and responded by taking the final frame before the interval to give O'Sullivan plenty to think about.

That would be the last time the Bristol man was level, however, as O'Sullivan rattled off three frames in a row after the resumption.

The first of them should have gone Trump's way but he never looked comfortable with the pink on the black spot and stalled on 30. O'Sullivan cracked in 43 and then produced a brilliant snooker on the green from which his opponent could not escape.

Seven became eight as O'Sullivan made a punishing 93 to the yellow after Trump missed a routine red to the corner, and a run of 60 secured him the next after the world number three blinked first in a safety exchange.

Trump managed to claw one back, though, with O'Sullivan missing the green, and the pair left the stage ahead of this afternoon's second session between Ricky Walden and Barry Hawkins, with the former 6-2 ahead.