By Tom Fordyce
BBC Sport at Twickenham
From the shell-shocked England players trudging out of the dressing-room post-match like zombies, to the thousands of stunned fans who streamed away from Twickenham in silence, the question was the same.
How the hell did that happen?
The last time England had been beaten, three-and-a-half months ago on a similarly freezing night in Paris, they had gone down in glory, blameless in defeat, having exceeded the wildest of extravagant expectations.
This time, to the utter disbelief of the 82,000 in the ground, England threw away a game that - at 19-6 in their favour - appeared to be over.
Wales were teetering, waiting for the final push to send them over the edge. People were taking bets on how big England's winning margin would be, with the consensus somewhere around the 25-point mark.
England were inept at finishing the game off... they know that you have to hammer the final nail into the coffin
And then the madness began.
Experienced internationals started throwing the ball around like blindfolded netball players. Others suddenly developed bars of wet soap for fingers.
Even Jonny Wilkinson - the hero of those unforgettable Gallic nights last autumn - was affected, firing the worst pass of his career five feet past a dumbstruck Danny Cipriani.
In the space of 15 second-half minutes, Wales racked up 20 unanswered points, including two tries that were almost served to them on silver salvers.
England had managed to get through an entire World Cup semi-final against France and final against the Springboks without conceding a single try. Here they shipped two in three minutes.
For the home fans, it was like watching a nightmarish film where the swashbuckling hero stands over his stricken foe with sword raised, ready to administer the coup de grace, only for him to then trip over his own feet, drop his weapon and knock himself unconscious.
His surprised enemy then gets up off the deck and strolls off into the sunset with the treasure and the girl.
James Hook raises his arms in triumph as Gavin Henson looks on
The match stats told their own story. England won more ball in open play, made more line breaks and won 10 turnovers to Wales' two.
But they also made six errors from kicks to Wales' one, and made a staggering 17 errors in total compared to Wales' five.
Iain Balshaw was responsible for four of them, Wilkinson three - and before you knew it, Jonny had tasted Six Nations defeat for the first time at Twickenham.
Afterwards, England captain Phil Vickery looked like a man whose children had just crashed his vintage car.
"We saw some of the best rugby we've played for some time and also some of the worst," he said.
"We made the mistakes, and they rose to the occasion. They didn't even have to do that much. The harsh reality of international rugby is that if you make mistakes, you're going to get punished."
If anything, Balshaw cut an even more demoralised figure.
"It was five or six mistakes that we made that put Wales on the front foot," he said. "When you look back at those mistakes, that's where the points came from."
Coach Brian Ashton had asked for a "dynamic, flexible and more movement-based game" from his players. In the first half, he got it.
Toby Flood looked poised and languid, Balshaw made a brilliant break, Lesley Vainikolo gobbled up Wilkinson's cunning cross-kick. The forwards were in charge.
It should have been easy from there. England were playing a team who had failed to get out of the group stage at the World Cup, who hadn't won at Twickenham for 20 years and whose last visit had ended in an absolute thrashing.
But it wasn't. Wales, inspired by the brilliant James Hook, saw their opportunity and took it in gleeful fashion.
England have lost four captains to retirement since the World Cup, and in the last 25 minutes, it told.
World Cup-winning scrum-half Matt Dawson summed it all up as Warren Gatland's players jumped into each other's arms at the final whistle.
"England were inept at finishing the game off," he said.
"These guys play high-level rugby week in, week out. They know that you have to hammer the final nail into the coffin. They threw it away."