Mark Williams beat Matthew Stevens in a thrilling all-Welsh final to win snooker's World Championship in Sheffield.

The new world number one, who had been trailing 13-6 earlier in the day, produced a brilliant fightback to force his way back into contention in the evening.

And Williams held his nerve in a see-saw final session to triumph 18-16 and become the first Welshman to win the world title since Terry Griffiths in 1979.

"At one point it looked like Matthew was going to run away with it," said Williams, who becomes the first left-hander to win the world crown. "But I managed to keep in there and did quite well to come back."

Stevens admitted he had blown his big chance: "Everything looked good at 13-7 - but Mark played brilliantly to come back and that's why he's world number one."

The match, which was played in a superb spirit between two great friends, produced one of The Crucible's great spectacles.

Last year's runner-up looked to be heading for more disappointment when he trailed his 22-year-old opponent 13-7 in the afternoon session.

But anyone who saw the 25-year-old in action in his marathon semi-final, when he overhauled John Higgins' 15-11 lead by reeling off six frames in a row, will have known not to write him off.

And Williams halted the Stevens juggernaut and took the last four frames in the afternoon to reduce his opponent's lead to 13-11.

Stevens was still able to produce the vintage break-building that had taken him so far in the tournament and a 120 clearance gave him his fifth century of the final and 11th of the fortnight.

Nerves appeared to affect Stevens, though, when he missed a straightforward red in the 31st frame and Williams took advantage to go in front for the first time since he led 4-3 on Sunday afternoon.

The pressure caused a string of awful mistakes from both players in the next 37-minute frame - comfortably the longest of the match - but Stevens finally edged it to pull level at 16-16.

But a superb break of 56 took Williams one up with two to play and he did enough in the next frame to claim the �242,000 winner's cheque.

50-62 28-84 (77 break) 56-33 23-103 (103) 65-18 76-61 (Williams 57) 123-0 (123) 35-75 (65) 24-64 37-91 (85) 21-59 0-117 (111) 7-114 (114) 79-6 (59) 22-73 (73) 68-0 (63) 0-133 (108) 48-66 106-0 (106) 54-55 81-0 (80) 79-34 71-46 79-37 77-33 (77) 0-67 (67) 75-6 74-0 (67) 16-120 (120) 61-13 70-66 29-60 76-8 (56) 73-21