Graeme Dott became just the second man in World Championship history to make a 146 break as the resurgent Scot took charge of his semi-final against Mark Selby.
The 32-year-old from Larkhall, just outside Glasgow, had entered his clash with Masters champion Selby as the underdog, with his opponent tagged as the tournament favourite.
After winning the opening session 5-3, Dott maintained his dominance to open up a 10-6 lead, and requires just seven more frames today to secure a third appearance in the Crucible final.
By reaching the semi-finals in Sheffield he guaranteed himself not only a top-16 ranking but another shot at world title glory.
The 2004 runner-up secured a first Crucible crown in 2006, beating Peter Ebdon, and on the evidence of the first two sessions against Selby he is playing well enough to win again.
Dott's masterful near-maximum effort came in the 13th frame, taking an early pink before following each other red with the black.
Until this World Championship the event had never seen a 146 - there have been nine 147s — but Northern Ireland's Mark Allen made one in his second-round match against Mark Davis to create history.
Unless there is a maximum, Allen and Dott will be sharing the £10,000 top break prize.
Selby lost the opening frame to Dott yesterday afternoon despite having a break of 54, but the Leicester potter fought back in the next with a run of 63, after an earlier 66 from Dott looked to have made him favourite.
Selby closed the gap to 6-5, however Dott then took over the heavy scoring, making an 84 break to restore his two-frame advantage before gunning in the 146.
The next frame was less memorable, Selby taking a low-scoring one but Dott battled back from 52 behind to win the penultimate of the session with a break of 66, and then capped his afternoon with 86 to develop his healthy lead.
Earlier, Australian Neil Robertson started and finished with century breaks — a total clearance of 140 and 104 — as he retained a four-frame advantage over Essex's Ali Carter in the other semi-final.
Robertson was 10-2 in front only for Carter to rally in last night’s session to close the gap to 15-9.
The Aussie, however, is only two frames away from making the final.