WHAT is it about the Ospreys? They consistently disappoint on big Heineken Cup occasions and yet they have a hoodoo hold over the team now acknowledged as the finest club side to have graced the European game.
And they adore playing at the RDS. The Ospreys kyboshed Leinster in the league final here two years ago, snatched victory with a late try and conversion on their last visit to Ballsbridge in March and, yesterday, they once again snuck up on the European champions when they were supposed to be fading and whipped away the home side's dreams of a Heineken Cup-RaboDirect Pro12 double.
And, they were not even on top of their game, as Shane Williams -- their two-try hero who produced the perfect valedictory performance in his final game for the Ospreys -- conceded afterwards.
"It wasn't our best performance, but you could see how much we wanted it at the end," said Williams. "It is a great way for me to finish. I am so proud to be associated with the Ospreys -- we have had some ups and downs, but it's fantastic to finish with some silverware. I will never forget this day."
If the diminutive winger was the headline-grabber, he had plenty of colleagues who can share his pride in this victory, including their excellent back-row, centre Ashley Beck and, in particular, Dan Biggar.
The out-half was central to those wins in 2010 and in March and it was his nerveless conversion of Williams' second try that clinched the deal.
Isa Nacewa, who also grabbed two tries in a superb all-round display, was awarded Man of the Match, but this decision seemed to have been based on Leinster winning, as it turned out, the award could have justifiably gone to Biggar.
While last season's final was a game too far for Leinster, who were mentally and physically drained from their Heineken Cup final win over Northampton when they faced Munster at Thomond Park, this time they were fully focused.
As well as Nacewa, Jonathan Sexton, Jamie Heaslip and Devin Toner had big games, while Brian O'Driscoll showed some lovely touches, notably in setting up Sean Cronin for Leinster's first try.
Being without Sean O'Brien and Cian Healy did not help, nor did losing Mike Ross to a hamstring strain after 13 minutes, but this defeat was not down to injuries or an inconsistent performance by referee Romain Poite, it came down to excellent application by the Ospreys and their ability to exploit Leinster weaknesses.
The Pro12 is often compared unfavourably to the Heineken Cup in terms of occasion and intensity, but this was a full-on affair, emphasised by a scuffle just before half-time which seemed to continue into the tunnel as the teams jogged off.
With summer tours looming, neither Wales nor Ireland need repercussions, but it did not seem to be major affair.
After the home side had done superbly to hold off the Ospreys following almost seven minutes scrum siege on their own line to go in 17-9 ahead, it was the Welsh side who came out more fired up.
Ashley Beck took advantage of a defensive lack of concentration for a soft try by the posts and though Leinster kept trying to pull ahead, Nacewa pouncing for his second score after his wondrous claim from a drop-out in the first half, Ospreys refused to be shaken off.
Two sin-binnings, for props Heinke van der Merwe and Ross' replacement Nathan White, contributed to the tries for Beck and Williams and captain Leo Cullen conceded that he struggled to come to terms with Poite's interpretations.
"He didn't really want to talk to me today which was pretty frustrating," said Cullen.
"We got an award for the least yellow cards in the Pro12 this season and then we give away two in the final.
"There were a lot of things from the game that I was left scratching my head about, but all credit to the Ospreys, I thought Biggar showed unbelievable character with that kick at the end."
The scrum was a major issue throughout, as the combination of Ross' departure, and Poite's interpretations frustrated Leinster, while the Ospreys felt they should have had a penalty try before half-time.
Coach Joe Schmidt could not mask his disappointment, particularly as there had been a communal desire to win this title to honour the contribution of the all the squad members who had toiled through the league games when front-line players were not available.
"I'm pretty gutted," he admitted. "There's inevitably frustration when you lose, we had two props sin-binned and there were a couple of decisions in the build-up to the last try.
"We knew Ospreys were going to come back at us and they deserve a fair bit of credit for doing so. They put a lot of pressure on our set-piece, the fact that scrums were going straight to ground.
"That was a source of massive frustration for us because we couldn't get a platform to play our game and then when we were down to 14 men, they took full advantage -- they have some really nice players.
"I certainly think the shoulder above hips is a major issue with the scrums, if you look back at it, you could work out if the scrum is working or not. The responsibility is on the two teams to scrum properly and then on the official to make sure that they do."
The New Zealander has been a stunning success since he joined Leinster in 2010 and it is a pity this reverse will take some of the gloss off what has been a wonderful season for Schmidt, his coaching colleagues and players.
It will hurt for a while, undoubtedly, but Leinster should reflect on the fact they have established themselves as Europe's finest club team and have the capacity to continue in that role for the foreseeable future. In that vein, Cullen is already projecting ahead to next season. "We're just trying to be a consistent team week-in, week-out," he said.
"It is going to be hard to put this one out of my head, but it is just about starting the process all over again. We will hear our (Heineken Cup) group for next season in a couple of weeks."
They should pray it does not include the Ospreys.
LEINSTER -- R Kearney; F McFadden, B O'Driscoll, G D'Arcy, I Nacewa; J Sexton, E Reddan; H van der Merwe, S Cronin (R Strauss 52-67), M Ross (N White 13); L Cullen (capt, B Thorn 45), D Toner; K McLaughlin (J McGrath 39-46), S Jennings (D Ryan 73), J Heaslip.
OSPREYS -- R Fussell; H Dirksen, A Bishop, A Beck, S Williams; D Biggar, R Webb (K Fotuali'i 55); P James (R Bevington 65), R Hibbard (S Baldwin 73), A Jones (A Jarvis 73); A-W Jones (capt), I Evans (J King 65); R Jones, J Tipuric, J Bearman.
REF -- R Poite (France).