Simply put, the Welsh war room outmanoeuvred their Irish counterparts before this match even got under way.
A great victory for Warren Gatland over Joe Schmidt then, but this defensive masterclass had Shaun Edwards's fingerprints all over it.
“Aw, mate, it was all about heart, effort and showing up,” said Edwards in one breath before revealing that Wales had been prepared for Schmidt’s ground troop, full frontal assault.
“I knew that Ireland would change their tactics today. Didn’t think they wouldn’t play the aerial game as they did against England. And that’s what I told the lads, we’re going to have to make 150 to 200 tackles.”
He didn’t know the full total.
“I knew they’d come up at us with ball in hand, they’re hard to turnover because they have a structured clean-outs system so you have to tough it out for long periods.”
Wales defended their try line from two ferocious, sustained assaults lasting a total of nine and a half minutes.
Afterwards, as Irish players stream silently down the Millennium Stadium steps and out towards their bus, Edwards refused to accept the plaudits laid at his feet.
He stalled to commiserate with Eoin Reddan, a former student from his Wasps days, and Tommy Bowe, from the 2009 Lions tour. Men blessed to have come under his esteemed tutelage.
Remarkably the CV might be dusted off again. "It was a very emotional game for everybody. Only the Six Nations can bring out the emotion like that, especially for myself because this could be my last Six Nations game with Wales with our contracts being up after the World Cup.
“If it ends up that way, it would be a great way to sign off.”
A tactical victory then?
“Ah no. It was a victory for a team effort and the fitness staff as well, for us to keep tackling for that long, it takes a fit team to do that.
“Number one we kept getting off the floor quickly, which is a massive part of your defence. If you are on the floor you are out of the game in rugby union. We got up and got into position really quickly. There is a mental and physical aspect of that as well.
“I thought our tackling, our leg chops, was of the highest order. I did say during the week we were going to have to tackle up to 150 times because of the way Ireland attack. It proved to be right.”
Have you ever seen so many tackles in a Test match? “I’ve not seen the total yet. 289. 289. Shows what I know really.”
Seventy five from the Welsh backrow (Sam Warburton 30, Toby Faletau 24 and Dan Lydiate 21). Edwards's boys.
“I did speak to the backrow about 20 minutes beforehand – I’d be close to all three of those lads. They knew they were up against a really world-class backrow in the Irish trio, who in the last two matches probably slightly got the better of us. But we were ready today. I put the challenge out to them three and I thought they responded.”
The previous Six Nations record of 245 tackles, by Italy in their comprehensive defeat to Ireland last season, was beaten by a resounding 44, season defining, hits.
All told, it was bad timing for Ireland. Lots of indefinable factors dragged victory from their reach. Like Edwards, their adopted English man who Paul O’Connell credits with evolving the game as far back as Wasps’ unrelenting dismissal of Munster at Lansdowne road in 2004, is on the verge of leaving.
Where does this rank in terms of the great defensive performances, Shaun? “That’s not for me to say. It’s for you esteemed gentlemen. I’m just proud of them.”
Two hundred and eight nine. Charteris's 37, the backrow landing 75 mostly lower leg chops, four lineout steals, surviving the loss of Sam Warburton for 10 minutes (and only losing that period 6-3). Losing Jonathan Davies at the end and surviving. Losing your tighthead prop to injury early on.
And your veteran loosehead at half-time. And your sub hooker to concussion.
It ranks right up there.