Ronnie O'Sullivan was marching relentlessly towards his first Embassy World Championship final as he opened up a six-frame lead over Joe Swail in the semi-final in Sheffield tonight.
The Rocket started the third session 10-6 ahead and won three of the four frames before the interval to extend his advantage to 13-7.
That left him needing to win just four of the remaining 13 frames to see off the challenge of the Irishman.
O'Sullivan was not at his best and won two of the frames on the final black after some sloppy play by his opponent cost him dearly.
Swail has been renowned in this tournament in coming back from tricky situations against the likes of Sean Storey, Mark Williams and Patrick Wallace.
He needed to make early inroads this evening if O'Sullivan was to be denied his first appearance in the world final.
But he got off to the worst possible start by losing the first frame on the final black after it had looked at his mercy.
O'Sullivan put together a run of 48 but Swail had only to pot the last three balls to cut his deficit.
He potted the blue but over-ran for position on the pink, missed his attempted cut shot and O'Sullivan edged home 62-59.
The next was clearcut with O'Sullivan just missing out on equalling the highest tournament break of 140 held by Swail and worth stg£20,000.
The Rocket raced to 133 but then found himself out of position on the black and he failed with an attempted double. Swail opened his account for the session in frame 19 when O'Sullivan missed the final red when leading 57-26 and let his gutsy opponent in for a 33 clearance.
But O'Sullivan again came from behind in the final frame before the interval to stretch his advantage to 13-7. Swail led 58-30 but a poor safety shot left the final red hanging over the centre pocket and he could shake his head as O'Sullivan made a 31 clearance. PA