Irish undone by missed chances
Wales 23 Ireland 16
This defeat in Cardiff is likely to live longer for Ireland than any of the 10 wins that preceded it.
Saturday was an opportunity lost for Joe Schmidt's side and the reason they passed up their shot at history was their failure to take their chances.
Wales gave a defensive performance of historic proportions, making a Six Nations record 250 tackles, with Luke Charteris shattering Serge Betsen's individual benchmark of 27 by going four better.
They deserve credit for their fitness, strength and aggression, but Ireland made it easy for them at times.
The champions arrived in Cardiff but didn't start playing for 15 minutes. At that stage they were 12 points down and another glance at the record books shows that just five teams have managed to bridge a gap that big since 2000.
What will frustrate them even more is that they figured out what was going wrong and completely changed tack mid-game, earning favour with a fussy referee who penalised them repeatedly for the same offence early on but sin-binned a Wales player before half-time.
Wayne Barnes' special topic for the opening half was rolling away and he repeatedly pinged Irish players repeatedly for their efforts. Leigh Halfpenny gleefully obliged.
Before he left the fray for a 10-minute breather, the inspirational Sam Warburton picked off Rory Best's throw when Ireland were gearing up for a maul five metres from the Welsh line. Opportunity knocked and Ireland turned the other cheek.
With the Wales captain in the sin-bin, his team showed remarkable composure; winning a dubious scrum-penalty and engineering a drop-goal for Dan Biggar. Johnny Sexton managed two penalties to make the score 15-9 and it was all to play for after half-time.
What followed was an epic 40 minutes that must have left the Millennium Stadium officials glad they'd left the roof open because it might not have survived the cacophony.
The loudest cheer greeted Wales' stubborn refusal to budge when Ireland set up camp in the 22, grounding and pounding for first 22 and then 38 phases without breaching the red wall.
Schmidt was unhappy with the leeway Barnes afforded the Welsh at the breakdown, while the hindmost foot law was abandoned but you had to admire the relentless nature of the defence. Worryingly, Ireland lost shape, an off-colour Sexton didn't take command of the situation and they failed to identify that Biggar was injured in the defensive line.
"We showed fantastic endeavour but that accuracy is what we're going to need and that's what we'll work on this week," the coach said. "We didn't quite get our rhythm and if you don't quite get that right against a defensive side that Wales have, particularly their ability to be very physical.
"It's often harder to load an attack than it is to load off a tackle defensively because you're getting off the line and aiming at someone whereas they've got to transfer a small oval shape amongst themselves to try and create a space and make sure they don't get knocked backwards. I felt we did a lot of that right and not enough of it right to convert it into points."
Not only did Wales escape, they marched down the other end and managed to do what Ireland had made look so difficult; go through the phases and score.
The visitors might have escaped after Jonathan Davies' initial break was stopped by Tommy Bowe and Rob Kearney halted Halfpenny, before Biggar threw a wild pass into touch. Again Best's throw was picked off and Wales wouldn't be denied, maintaining their attacking structure far better than Ireland had minutes previously. Eventually, Jamie Heaslip rushed up on Biggar, allowing Scott Williams step inside Bowe to score.
Halfpenny missed his conversion to allow Ireland a sliver of hope and, once again, they managed to get into the Welsh 22 and earned a penalty five metres out. Eoin Reddan decided to tap when the scrum might have been the better option. He was stopped short and with both half-backs buried in the ruck, the forwards failed to notice the massive overlap on the right wing and with Jared Payne and Bowe pleading for the ball, Cian Healy knocked on.
It was another glaring missed chance and, while they did earn a penalty try from their rolling maul with 11 minutes to go to narrow the score to four points, the clock was against the visitors.
Barnes penalised Healy for holding on and Halfpenny made no mistake to end Ireland's hopes of a win, but while the Grand Slam was gone, the draw would have maintained control of the Championship.
With Wales fatigued from their defensive efforts and Sean Cronin, Iain Henderson and Reddan upping the pace, Ireland went for a grand finale. Davies saw yellow for a cynical deliberate knock-on that denied Simon Zebo and, while Ireland messed up another lineout, they got a second chance.
This time, the maul came down but Barnes' arm stayed down too. Wales were awarded the scrum, but Ireland put the squeeze on and appeared to have won the ball when the English official gave the home side a penalty. Schmidt was clearly annoyed.
"I felt that we had massive scrum dominance and even that last scrum, from what I could see the ball was in our scrum," he said.
It wasn't to be, Cardiff erupted and the Championship goes to the final day.
Wales - L Halfpenny; G North, J Davies, J Roberts (S Williams 60), L Williams; D Biggar, R Webb (M Phillips 66); G Jenkins (R Evans h-t), S Baldwin (R Hibbard 58), S Lee (A Jarvis 12) , L Charteris, A Wyn Jones (J Ball 71), D Lydiate (J Tipuric 68), S Warburton, T Faletau.
Ireland - R Kearney; T Bowe, J Payne, R Henshaw, S Zebo; J Sexton (I Madigan 75), C Murray (E Reddan 67); J McGrath (C Healy 55), R Best (S Cronin 60), M Ross (M Moore 60), D Toner (I Henderson 62), P O'Connell, P O'Mahony, S O'Brien, J Heaslip (J Murphy 72).
Ref - W Barnes (England)