Mark Williams hit form to build a commanding 6-2 lead in his Betfred World Championship quarter-final showdown with five-time champion Ronnie O'Sullivan.
The Welshman, seeking a fourth world title of his own, won five consecutive frames to establish his advantage heading into the overnight break.
The veteran duo shared the first four frames before Williams found his stride, making a break of 72 to move two clear.
Williams continued to enjoy the better of his opponent as he capitalised on a missed pink from O'Sullivan to extend his lead to 5-2.
Then, in the final frame of the session, Williams recorded a brilliant break of 130 to stretch his advantage to four frames and leave O'Sullivan with work to do when play resumes.
Anthony McGill was even more impressive in building up a 7-1 advantage over Kurt Maflin.
Earlier, Kyren Wilson took a 5-3 lead over defending champion Judd Trump. They resume from 7pm, as does the match involving Mark Selby and Neil Robertson, with the latter 5-3 ahead.