Shane Williams squeezes in for his second try against Scotland

"It's 100% certain that I scored it, there's no doubt in my mind," the wing told BBC Radio Wales.

"I managed to break the line and decided to go round the full-back not step him. It's great to get on the scoresheet, I wanted a big game.

"Scotland were disciplined while we only played in patches. We need to learn from that, but we finished well."

Highlights: Wales 30-15 Scotland

Interview: Scotland coach Frank Hadden

Interview: Wales coach Warren Gatland

Interview: Man-of-the-match Martyn Williams

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Wales coach Warren Gatland said he was very pleased at the end of a "nerve-wracking" game, his first in charge in Cardiff, but admitted his team still needed a lot of improvement.

"There was only one team that deserved to win and that was the team in red that played all the rugby," the New Zealander said.

"Not too many rugby players in the world could have scored that second try that Williams got.

"It didn't feel like Scotland looked like scoring, the only method of scoring was through the boot of Chris Paterson so I think we thoroughly deserved to win - although there's a lot of improvement to do in this team."

Williams himself was aware that no-one's place in the side is safe ahead of the home game with Italy in two weeks time.

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"Warren's showed he's not frightened to change things," said the wing.

"It's obvious that not everything was right, and I'm sure he'll address that."

Man-of-the-match Martyn Williams was delighted to seal the victory and build on last week's stunning triumph over England at Twickenham.

"It was vitally important, if we hadn't backed up last week's result it would have been a huge anti-climax," said the flanker.

"A few 50-50 bounces are going our way and at the moment we're having a little bit of luck, so long may it continue.

"But Shane's try was never in doubt, the effort deserved a try!

"That was a great finish, a world-class finish and I think it was the crucial point of the game."