A Triple Crown and a triple farewell are on the agenda at the National Stadium, Cardiff this afternoon.

If England beat Wales, and it is hard to make a convincing case against them, then they will lift the mythical prize having already disposed of the Irish and the Scots. They may even take the Five Nations' Championship as well, depending on events in Paris.

However, whatever happens, three of the most outstanding performers of their generation will be bidding an fond international farewell, though one of them may only do so from the replacements' bench.

Will Carling, Jonathan Davies, and Rob Andrew will be taking a final bow.

What a mark each of them has made, not entirely on the field of play.

Carling, for so long captain courageous, the man who labelled the RFU committee ''a bunch of old farts,'' was probably rugby's first millionaire from related earnings, and certainly the game's most adventurous romancer, will be wearing the red rose for the seventy-second time.

''I have had a good innings,'' he said yesterday, ''and although I want to go on playing at a club level, there are other things I wish to do with my life.'' They are unlikely to be done quietly.

Davies, apart from Barry John, the finest fly-half I ever saw, is recalled for his thirty-second and last cap to face the same opponents against whom he made his debut 12 years ago.

At his best, he twinkled through defences like a trout up a stream; he is slower now and bulkier but still a man of magic.

Jonathan went to rugby league because he wanted to be paid for what he did brilliantly. Ironically the big money has arrived in union as his body has called it time.

''I am thoroughly looking forward to ending my career against the English. There have been difficult periods but I reckon I am lucky.'' And we to have been around to see him.

Rob Andrew is absolutely astonished to be here at all. Coach Jack Rowell summoned the 34-year-old from his desk as Newcastle's director of rugby as back-up to Mike Catt.

The move has prompted bitter criticism from the likes of Wasps' Nigel Melville and Harlequins coaching director, Dick Best.

''Not much surprises me in this game,'' observed Best, ''but I am staggered by this. It is Rowell hitting the panic button and it smacks of self-preservation.

''What sort of message does this send to young players?'' An infuriated Rowell blasted back. ''I really cannot understand why former England managers and coaches criticise team selection in the run-up to an international.

''Rob is here because he can still do the job, if required.

''If there is a more reliable goalkicker still playing I have not seen him.''

Andrew wisely takes diplomatic immunity. ''I was asked if I would help out my country and agreed. The decision was not mine and it is simply a one-off.''

England will probably win without him but it would be a nice gesture if Andrew was sent on for the last 10 minutes. His contribution over the years may have been less spectacular than the other two but probably more effective in terms of match winning.

The Welsh are now talking bravely yet they cannot be confident.

Five of their best players have failed the doctors' scrutiny, and backs like Ieuan Evans and Scott Gibbs are not easily replaced.

For an hour against France, England looked absolutely invincible. Then they just lost first concentration, next two tries, and finally the match.

It was the kind of collapse one has come to expect of their cricket team. I do not expect a repeat.

Rowell has made one smart selection move, bringing in Austin Healey, of Leicester, to the scrum-half spot. That will give Catt the kind of service he requires to move his line.

The England backs, and some of the forwards, will be out to impress the Lions selectors and none will be more determined than captain Phil de Glanville, so far ignored by Fran Cotton and Co.

It is certainly bound to be an emotional occasion. Not only are the three greats disappearing, so is the stadium itself.

Workmen will begin tearing it down and start erecting a new one, almost but not quite on the same spot, within 24 hours after today's final whistle.

There will be lumps in a few throats. Maybe lumps in a few pockets, too.