David Byas was entitled to his wide grin for proving the Doubting Thomas's wrong as Yorkshire overwhelmed Glamorgan by 328 runs at Swansea yesterday to increase their lead at the top of Division One of the CricInfo Championship.

It was the joint fourth-highest winning run-margin in York-shire's history, and the biggest in 54 years, but it would not have been achieved if Byas's critics in the media had got their way.

Because of a bad weather forecast he was slammed for not enforcing the follow-on and again for deciding to continue Yorkshire's second innings in faint drizzle yesterday morning when the lead was already 384.

But the clouds rolled back and Byas was able to register his first century in three seasons before declaring at 277 for seven with a colossal lead of 453.

Then Gavin Hamilton made hay to snatch five for 27, his best analysis since 1998, and there were still around 40 minutes to go to tea when Glamorgan's last wicket fell at 125.

Byas was 64 not out at the start of play and mainly with James Middlebrook he helped add 69 in an hour to finish unbeaten on 105 from 162 balls with 11 fours and a six. It was his first ton since his Roses century at Headingley in 1998.

Whereas Chris Silverwood had demolished Glamorgan in the first innings, it was now the turn of Ryan Sidebottom and Hamilton.

Sidebottom began it by having Jimmy Maher lbw offering no stroke and finding the edge of Mike Powell's bat before Hamilton stepped in, bowling Matthew Maynard and Steve James.

Glamorgan looked demoralised when they went off for lunch at 52 for four and on the resumption Sidebottom had Adrian Dale neatly picked up at third slip by Scott Richardson.

He also accounted for Keith Newell, and Hamilton returned to the fray with three wickets in four balls.

Yorkshire have now won three of their first five matches and are the team that everyone else is chasing but coach Wayne Clark is aware that they had an identical record at this stage last season before slipping.

This was Hamilton's first Championship game of the season after being sidelined with sore shins and he was delighted to return astonishing match figures of seven for 42 off 17 hostile overs.

"I was a bit wide at first but having played a game or two for the second team helped and it was not long before I settled down," he said."

Although Craig White did not bowl he did turn his arm over in the nets in the morning for the first time since hurting his back.

White intends joining up with the England squad for more nets at Old Trafford today and if he feels up to it he will be allowed to bowl for Yorkshire in their Championship match against Kent at Headingley, starting on Wednesday.