By Tom Fordyce BBC Sport in Cardiff

Wales celebrate winning their second Grand Slam in four years

Barely had the broken glass and soggy paper flags been swept off the streets of Cardiff on Sunday morning when the carping began.

This Six Nations, I was told by several grumpy non-Welshmen, has been average in the extreme.

Their argument went like this: England were up and down like a flea on a trampoline. France were cavalier and collapsible. Ireland duller than a tax return. Scotland were turgid and Italy as one-dimensional as this full stop.

Grand Slams, by their very nature, are not won by average teams

Even ignoring the wonderful story that has been Wales' unexpected renaissance, it is an argument that holds less water than a colander.

A championship that comes down to the final match of the season, with the top two teams locked together at 9-9 with 20 minutes to go and a Grand Slam hanging in the balance, can never be described as average.

Was the standard of rugby scintillating throughout? No. But for drama, sub-plots and tension, 2008 was a year to savour.

When even the Wooden Spoon battle comes down to the last minute, you know it is no ordinary year.

To those who might claim, as some did in 2005, that Wales' Grand Slam came in the absence of a challenge from any other decent team, there are several retorts.

New coaches Gatland (left) and Edwards have transformed Wales

Grand Slams, by their very nature, are not won by average teams. England's dominant side from 1999 to 2003, the same group that won the World Cup, managed only one in all that time.

Wales earned this Slam the hard way - by winning at Twickenham for the first time in 20 years and in Dublin for the first time in eight years.

They played with a mixture of pragmatism and flair that their rivals could only dream of, gathering momentum with every match and dragging records along in their wake.

Every time a challenge presented itself, they rose to the occasion. Thirteen points down to England, they turned the game on its head. With Italy pressing hard at half-time, they accelerated out of sight.

Down to 14 men twice against Ireland, they closed the game out with flinty-eyed professionalism. Level with France with 60 minutes gone, they conjured up the chances to pull clear.

The other contenders were no limp-wristed walkovers. England were coming off the back of a World Cup that resulted in them being 10 points short of winning the thing.

France were devastating against Scotland and, in patches, elsewhere. Ireland looked good against Scotland and, sometimes, France.

England uncovered a potential superstar in fly-half Danny Cipriani

In a season of transition for each country - half the teams with new coaches and half in desperate need of revitalising - Wales coach Warren Gatland pulled off the trick better than anyone else.

His task now is to ensure that his squad builds on the achievements of the last two months over the next two years.

No-one needs reminding that the last Grand Slam was followed within a year by the coach's resignation, the captain losing it on national television and only two wins in the next 10 Six Nations matches.

And with the summer to be spent taking on the world champions on their own patch, Gatland's 100% record will be tested to the full.

Yet there is every reason for Welsh fans to be more optimistic this time around. Gatland's brand of rugby is several times more robust than the champagne version of 2005, with a defence as parsimonious as anything the game has seen.

In Martyn Williams and Ryan Jones he has two of the best forwards in the world and in Mike Phillips and James Hook a pairing that could hurt any team. Shane Williams and Lee Byrne are Lions shoe-ins, while his centres are so special a pairing that their record together reads: started 12, lost 0.

606: DEBATE Do Wales deserve to be 2008 Grand Slammers? Poshishvalleygirl1

Fresh talent is also coming through the junior ranks, with teenage fly-half Dan Biggar and Scarlets centre Jonathan Davies leading a crop of players that has Neil Jenkins purring like an old puss.

Gatland himself believes Wales will not peak for another two years. He also says that they are currently a couple of levels below the southern hemisphere teams and points to the need to convert the sort of half-chances that sometimes went begging this season.

You would expect him to say that. It is the sort of clear-eyed detachment that has served him so well in the job so far.

But for now, with the Grand Slam parties still going strong in some parts, he should allow himself a little time to wallow in the achievements of his anything-but-average team in an anything-but-average year.