Wales wing Shane Williams celebrates his crucial try in Ireland

Williams claimed his 40th Test try in Saturday's 16-12 win in Ireland to equal Gareth Thomas's Wales record.

That clinched the Triple Crown to set up a second Slam attempt in four years.

"Shane petrifies people, he's got that 'X-factor' and that's what we've got over and above some of the other teams at this moment," Evans told Scrum V.

"When you're a winger, an attacking player, when you're on form and full of confidence you worry defenders who are constantly having to think what you're going to do.

"Once you put doubt in defenders' minds you really have an advantage and he's capitalising on that at the moment."

606: DEBATE What can one say about Shane? His try-scoring has been awesome and I can't wait to see him overtake Alfie's record shadthameslover

Evans scored 33 tries in 72 appearances for Wales during his career, while Williams now has the phenomenal strike rate of 40 in 55 Tests after his score at Croke Park that ultimately proved the difference between the sides.

Evans believes Williams's record stands up to scrutiny against any of the wing greats to play for Wales and says that the 31-year-old has still not reached his peak.

"Scoring 40 international tries takes some achieving and it's an indication of the talent he's got," Evans added.

"That tells you everything you need to know and I think there's a few more on the way.

"He's also taken on some guidance from Wales coach Warren Gatland and assistant Shaun Edwards and improved elements of his game.

"Shane was getting turned over in contact, he's worked on it and that's what you want for players - to develop and grow.

"So he's constantly aware that he has to improve to stay at the top but at the moment he is on fire."

But while Williams is getting the lion's share of the headlines, Evans says it is the way Wales are now playing under new coach Gatland that is giving him the scoring opportunities.

Wales are now more streetwise in their play Ieuan Evans

That team effort has been underpinned by a combative pack and a ferocious Edwards-inspired defence.

The combination has now engineered a likely championship title - France must beat Wales by at least 20 points in Cardiff to overtake them - and quite possibly a second Grand Slam in four years.

"Wales are now more streetwise in their play under Warren Gatland and it's an area in which we've often been quite weak," Evans said.

"You have to earn the right to go wide and that's the mantra he keeps hammering home

"They seem to have matured very, very quickly.

"Going to Ireland was a real test and Wales stood up tall, it was a professional performance.

"Events have helped us along the way, other teams have imploded as we've grown, but great!

"You can't detract from Wales' improvement and Warren Gatland was pretty honest in his appraisal that it will be another couple of years before this team can set the world alight.

"But so far you can't possibly fault it."