Rocket Ronnie turns on the style as former champion takes charge against Williams
16:41 GMT, 29 April 2012
Crucible showman Ronnie O'Sullivan turned on the style as he went close to thrashing Mark Williams with a session to spare.
Williams took the final two frames of the session to guarantee they must return on Monday evening, but the Welshman is surely destined to lose to O'Sullivan at the Crucible for the fourth time in seven years.
The pair have met in 2006, 2008 and 2010, with the result going O'Sullivan's way each time, and this time he has armed himself with an imposing 11-5 lead in their best-of-25-frames match.
Nearly there: Ronnie O'Sullivan leads 11-5 against Mark Williams
It has been a decade since Williams last beat O'Sullivan, with that success coming at the Thailand Masters.
Once O'Sullivan came from 3-2 behind to lead 5-3 overnight, the omens were not good for Williams, and his hopes were soon in tatters as the frames raced by once they resumed.
There were two sparkling centuries amid a barrage of blistering breaks, with O'Sullivan running through his repertoire of shots long and short, spins of all imaginable type, and no little shrewd safety.
O'Sullivan was terrific in each of the afternoon's opening four frames, although he often had Williams' mistakes to thanks for his opportunities.
In the first, Williams missed an attempted plant to let O'Sullivan in for a break of 107.
Mountain to climb: Williams cannot afford any more slip-ups
The gap went to three frames, and it was soon four. Williams was put in deep trouble behind the brown, and played the white off the side and top cushions but the wrong side of his intended target red, missing all the balls and leaving an easy starter.
O'Sullivan had a plant red in a break of 74, and Williams could only stew in his seat.
A 51 guided O'Sullivan towards an 8-3 lead, before a 68 took him to the interval four frames from victory.
The genius was still at work when they returned, firstly with a 128 which was followed by a sprint to 93.
That made it nine frames in a row for the 36-year-old from 3-2 behind, and a free Monday evening was by that stage looking a probability.
O'Sullivan had chances early in the 15th frame too, but two reds were not followed by colours and Williams seized his chance, making 86 to guarantee him another night in Sheffield.
Williams had never lost a Crucible match with a session to spare, so to keep that record intact was his consolation from a miserable afternoon.
The 37-year-old Ebbw Vale man, champion at the Crucible in 2000 and 2003, scrambled through what proved easily the scrappiest frame of the session to trim O'Sullivan's lead to six frames.
The most recent of O'Sullivan's three world titles came in 2008, when he beat Williams 13-7 in the second round.
This time the margin could be heavier, with the performance leaving no doubt he is in the mood for a fourth Crucible crown.