Two-times champion Williams was edged out 10-9 in his match against Northern Ireland's Joe Swail while world number two Doherty crashed out 10-7 to Swail's fellow countryman Mark Allen, a qualifier making his Crucible debut.

Irish cuesman Ken Doherty, seen here in 2003, has become the third former world champion to fall in the first round of the snooker world championships here as he went out 10 frames to 7 to debutant Mark Allen. [AFP]

Swail, who has twice reached the semi-finals at the Crucible, rated the win as "among the best" in his career.

"He's one of the best players in the world, so I'm delighted," said Swail.

Williams had no complaints about the result, saying: "I just didn't play at all. He was the better player all day and deserved to win."

The defeat comes at the end of a poor campaign for Williams.

"I'm disappointed with the way I've performed over the season more than anything," the 32-year-old Welshman told reporters. "It's probably the worst season I've ever had."

Doherty, winner of the title in 1997 and twice a runner-up, drew level at 7-7 with Allen after being 6-3 down overnight, but Allen then won the next three frames to seal a remarkable 10-7 victory.

Allen faces Matthew Stevens, twice a beaten finalist, in the second round.

Scot Stephen Maguire, who thrashed English qualifier Joe Perry 10-3, played down his chances of lifting the title.

"I'm not playing well enough to win it just now," said Maguire. "I'll have to improve through the tournament."

Stephen Hendry, winner of a record seven world titles, came back from 5-1 down against David Gilbert to cut the qualifier's lead to a solitary frame at 5-4.

Stephen Lee has a slender 5-4 lead over fellow Englishman Mark Selby. The best-of-19-frames match plays to a finish on Wednesday.