The game's decisive moment, when it came, was dominated by Wayne Barnes.
The Englishman's decision to penalise Robbie Henshaw, as Ireland inched towards the try line, ended a ferocious period of pressure on a flagging Welsh defence.
Henshaw roared in Barnes’ face. The referee ignored the young centre, ignored all pleas for mercy.
The decision was made.
“Rory, let me explain,” said Barnes, waiting for the Ireland captain to reappear from underneath a mass of jubilant Welsh players.
Of course, unlike 2015, Barnes was not the villain here; the call was correct as Henshaw’s entry, from in front of the ball, reignited a stalling Irish drive was clearly offside.
Nor should Henshaw shoulder blame for the defeat (one mistake is eradicated by 15 horrendously punishing carries coupled with 14 tackles and a turnover).
"(Henshaw) has engaged in front of the ball," said Wales coach Rob Howley.
“It is clear and obvious as far as we are concerned. I think it is a testament to both teams that played a high octane game - that should be applauded.”
Howley was asked if the Irish attack was predictable enough to deny them a try.
"A Joe Schmidt side predictable? Come on, man. They are a quality attacking side it is testament to our defence rather than their attack."
But, with Ireland trailing 15-9, that failed drive - Ireland’s primary weapon under Schmidt - proved a seminal moment.
"We are bitterly disappointed," said Rory Best. "But when we look back on it we only have ourselves to blame. Wales are a quality side but we made a lot of errors. We made a lot of mistakes and had chances to get in front and bar 6-5 we never got in front, never dominated the game on the scoreboard, which is disappointing as there were chances in their 22 that we didn't convert."
“To not score, for us, is very disappointing. It is devastating. We were expecting to win.
“We had chances and we let them off the hook.”
The Welsh sang into the night as only they can. Howley was a heroic figure in the Valleys before stepping into this second stint as the interim (that cursed word) coach, while Warren Gatland is busy constructing a Lions panel for New Zealand this summer.
This will help Gatland’s cause as much as it will Wales and equally cast doubt over Irish certainties.
George North’s general well being was questioned after a poor performance against Scotland. The 24 year old has a worrying recent history of concussion but any lingering, certainly immediate, concerns in that regard were dispatched by this wondrous two try show.
“We’re funny in Wales,” said Howley. “When you praise guys too much, they sit back, but if you criticise, they might go into their shells. It has been a tough couple of weeks for us all.
“The players have been very honest since the Scotland game. Honest about the hurt we all felt. They wanted to go out in front of probably the best supporters in world rugby and give a performance they can be proud of.
“I think they did that; they out scored one of the best sides in world rugby three tries to nil.
“We kept them out.”
