Williams once again provided the decisive moment with the try that put Wales on course for their 10th Grand Slam, 100 years and a day after their first ever clean sweep. 

Williams’ 41st Test try broke the Welsh international record and sent Cardiff into a frenzy of excitement. 

After Williams pounced on a 60th-minute mistake from Yannick Jauzion to score under the posts, Wales pulled clear to record their biggest victory over France in Cardiff since 1950. 

Stephen Jones came off the bench to kick 10 points, on top of nine from James Hook, while Martyn Williams rounded off the win, and a magnificent individual performance, with a late try. 

But for the first hour Wales were given the toughest test of the championship. 

Huw Bennett missed his jumper at the first lineout, then Wales conceded an early penalty for offside and Lee Byrne decided unadvisedly to attempt a drop-goal from inside his own half. 

But they soon settled, with Martyn Williams pouncing on a loose ball and Gavin Henson a massive influence in the centre. 

Hook, preferred to Stephen Jones for his creative edge, sparked Wales’ first attack with a delightful flick outside to Shanklin. 

Mark Jones, in two minds whether to chip or pass inside to Byrne, lost his footing on the the greasy surface but Hook slotted his first shot at goal after seven minutes. 

David Skrela’s extraordinary restart went backwards and Wales needed no second invitation to keep the pressure on, with Henson again a midfield target and his neat offload sent Shanklin charging into the French 22. 

Untidy breakdown work gifted Jean-Baptiste Elissalde a simple shot at goal, which he accepted, but Hook slotted his third penalty to open Wales a 9-3 lead after the first quarter. 

After Hook’s attempted clearance was charged down, Julien Malzieu broke the first line but was quickly swallowed up by a swarm of scrambling Welsh defenders. 

Another break from Malzieu carried France to the edge of the Welsh 22 but Martyn Williams snaffled the turnover. 

France hammered away at the Welsh defensive line and Elissalde slotted a second penalty after Henson was sin-binned for a high tackle on flanker Fulgence Ouedraogo. 

By the time Henson returned France had drawn level, with a third penalty from Elissalde, after Hook had pulled a second attempt wide of the posts. 

With half an hour remaining coach Warren Gatland introduced Stephen Jones at fly-half - but predictably it was Shane Williams who conjured up the match-winning moment. 

Jauzion spilled the ball under pressure from Shanklin and Shane Williams pounced, hacking the ball forward twice before diving on it under the posts. 

Stephen Jones converted and then landed a penalty to move Wales two scores clear.

Dimitri Yachvilli caused a few nervous moments by pulling a penalty back for France but Jones slotted a second shot

Then, after Mark Jones had made a searing 80-metre break, Martyn Williams scored under the posts to send the Millennium Stadium into raptures.