Deasy penalty seals it for classy Lansdowne
Lansdowne 18 Clontarf 17
In the end, the league's most consistent team were crowned champions but Clontarf were left to rue the fact that they threw away a 17-8 second half lead.
Lansdowne produced a stirring comeback and their out-half Scott Deasy, in particular, showed admirable composure to kick the winning points after earlier throwing a wayward pass that the excellent Matt D'Arcy had intercepted to score a Clontarf try.
Both sides had players sin-binned in the second period and defending champions 'Tarf took full advantage of Adam Boland's 44th minute yellow card as they scored eight points without reply in a rampant spell.
Ariel Robles' yellow card for a fractionally late tackle in the closing stages was far more controversial and 'Tarf coach Andy Wood felt it was unjust.
"I thought was harsh. I thought it was a penalty at best. I was surprised to see a yellow card, absolutely," said Wood.
"It took a long time for a yellow card to be given. We were clearly on top from the first scrum. It was an area we thought we could definitely get some purchase from and we did. I don't think we were fully rewarded for it.
"Look, I'm not trying to offer up excuses, we did have a lot of territory and we did have a lot of chances, but there was a number of line breaks that we didn't finish off.
"We left everything out there, to come up a point shy of it is disappointing. We played all the games we could this season, we maxed it out," the Kiwi added.
Wood's side were dominant up front with newly signed Leinster prop Royce Burke-Flynn impressing all afternoon in front of a sparse crowd at the Aviva Stadium, but 'Tarf failed to make it count on the scoreboard.
Rob Keogh cancelled out Deasy's penalty with two of his own before Lansdowne struck for a well-worked try.
Deasy's cross-field kick was gathered by Tom Farrell and although the Leinster academy player's pass looked forward, Mark Roche collected it to cross in the corner for an 8-6 lead at the break.
The former Munster out-half's afternoon took a turn for the worse when D'Arcy collected his sloppy pass to streak clear seven minutes after the restart. Keogh missed the conversion but had already added a second half penalty as 'Tarf took a 14-8 lead.
Keogh made amends for his wayward conversion with a penalty shortly after and 'Tarf threatened to pull away but Lansdowne coach Mike Ruddock never panicked.
"I left my emotions in the semi-final so I just observed this one," he smiled afterwards.
"We've found the resolve to win a lot of those tight games this season. To dig in like that and get the result, I thought it was a formidable display by the boys.
"It's very pleasing. Clontarf have lost players too but the mainstay of their squad has stayed the same. We've got a lot of academy boys who we very often don't see until a Thursday so pulling them together can be difficult.
"We've had a catchphrase all season which is 'next minute'. You can't change what's gone on before. There's no point in us blaming someone for an intercept try or a yellow card. That's a waste of energy," said Ruddock.
Those wise words clearly worked when man-of-the-match Joe McSwiney was on the end of a powerful rolling maul to score. Deasy added the extras and fired over a brilliant match winning touchline penalty with 14 minutes left on the clock.
It was enough for Lansdowne to claim just their second ever Division 1A title on an afternoon that showcased why the club game remains a pivotal part of Irish rugby.
Lansdowne - C Kelleher (J O'Brien 16-25); M Roche, T Farrell, T Daly, I Fitzpatrick; S Deasy, A Griggs (T Kiersey 62); P Dooley, T Moran, I Prendiville (A Boland 29); B Moylett (T Beirne 50), S Gardiner; J McSwiney, A Conneely, R Boucher (capt) (P O'Driscoll 59).
Clontarf - R Keogh; C O'Brien, C O'Shea, M D'Arcy, M McFarland; E Ryan (T McCoy 39) (A Robles h/t), S Cronin (capt) (D O'Meara 75); I Soroka (I Hirst 58), B Byrne (R Litchfield 79), R Burke Flynn; T Byrne (C O'Keefe 60), B Reilly; K Moran, A D'Arcy, T Ryan (L Og Murphy 73).
REF - S Gallagher (IRFU)