By Dan Warren
BBC Sport at the Crucible
Mark Williams wasted little time as he sealed an impressive 13-7 victory over Stephen Hendry to reach the last four.
The win ensured the Welshman became only the second player to regain the world number one ranking after his countryman Ray Reardon.
Hendry began Wednesday's session with a brilliant 92, but Williams responded with an 81 to go 11-7 ahead.
The 2000 world champion then rattled off the two frames needed for victory, ending a match full of quality snooker.
Williams admitted to having mixed emotions after beating a close friend.
"Although he's a friend, when we are playing, I feel I want to beat him as much as I would anybody," he said.
I still think I can take the title again
"But when I shake hands with him at the end, I feel I'd rather have beaten somebody else.
"He wished me all the best for the rest of the tournament. 13-7 is a good result. I don't think I played too well, but I won a couple of scrappy games, which was important."
Hendry has not given up hope of winning the world title in the future, despite the defeat.
"I did not take my chances in this match, but I still think I can take the title again," he said.
"But if you don't play to your best in the quarter-finals, you go home.
"One of my aims this season was to get back into the top four and I've done that, but the world championship is the one everyone wants to win."
Quarter-final result: M Williams (Wal) 13-7 S Hendry (Sco)
55-57, 96-23 (84), 131-1 (131), 64-65, 115-5 (115), 0-76 (76), 89-1 (55), 77-64, 28-75 (64), 64-34, 5-71 (68), 72-39 (56) 1-111 (111), 82-12, 70-33, 80-0 (50), 46-92 (92), 81-0 (81), 62-22, 71-44