Mark Roche scored two tries and earned the man-of-the-match award as Lansdowne were crowned Ulster Bank League champions for the first time.
Mark Roche, a member of this year's Ireland Under-20 squad, plunged over for a bonus point score in injury-time as Lansdowne sealed Division 1A silverware with two rounds still remaining.
Mike Ruddock's men came into this match armed with a 19-point lead over second-placed Clontarf, and had the clear aim of winning the title on the Aviva Stadium's back pitch in front of the RTÉ television cameras.
Clontarf took a second minute lead though, Richie Lane punishing Tadhg Beirne for being caught offside with a superbly-struck penalty from wide out on the left.
The Lansdowne front row – comprising Jack O'Connell, Tom Sexton and Martin Moore – then made quite a statement with a ground-gaining scrum, that good work setting up a left-sided penalty that Craig Ronaldson sent wide from outside the 22.
Ronaldson, who had strapping on a thigh injury, soon got the Lansdowne attack going with prop O'Connell's angled run opening up the visitors' defence.
Cian Aherne, the division's most prolific finisher with 12 tries this season, also tested Lane's tackling out wide before Lansdowne forced a succession of scrum penalties five metres out.
Clontarf just about held out with number 8 Frank Cogan leading a breakout, but the territorial pressure built up by the headquarters club eventually told.
In the 22nd minute, a neat back-line move sparked by Ronaldson saw crafty centre Roche make an initial break and he popped the ball to the supporting Sean Carey who evaded two defenders on the way to the try-line.
Roche had a livewire presence in the Lansdowne back-line, charging through midfield again just three minutes later. Ruddock’s side kept pressing and Roche popped up in the left corner to score past covering full-back Matt D'Arcy.
It was a terrific one-handed finish by Roche and Ronaldson followed up with an excellent touchline conversion to make it 14-3 to the table toppers.
‘Tarf stormed downfield in response, pack heavyweights like Cogan, Ben Reilly and Mark Flanagan stepping up in the close exchanges.
On the half hour mark, Andy Wood's charges threatened from a five-metre lineout and a well-executed maul was rewarded with a try from the increasingly influential Cogan.
The margin was down to four points once more after Lane’s pinpoint conversion from the right, with a real tit-for-tat nature to the proceedings.
A lovely left-footed drop goal from Ronaldson steadied Lansdowne before the break, taking his huge haul for the league campaign to 203 points.
But another crisply-hit three-pointer from Lane maintained his 100% kicking record and reduced the arrears to 17-13 for half-time.
There was a cagey opening to the second period before big ‘Tarf prop Royce Burke Flynn intercepted a pass and his 30-metre charge almost resulted in a try.
That score duly arrived in opportunist fashion in the 47th minute when bustling flanker Simon Crawford broke away from a ruck to raid in under the posts.
Lane added the extras but Lansdowne were soon level thanks to a central penalty from Ronaldson, with Clontarf replacement prop Ben Barclay earning a yellow card for a needless charge on Clive Ross.
Clontarf’s strong lineout got them out of trouble while down to 14 men, however Lansdowne went close to a third try through the fast-breaking Roche.
In the very next phase, number 8 Ron Boucher duly picked up the ball at the base of a powerful scrum shove from the Lansdowne pack to dot down. Roche landed the conversion for a 27-20 buffer.
Out-half Darragh Fitzpatrick was denied a try in the left corner by a forward pass, as the north Dubliners showed no signs of wilting in a very physical encounter.
With two minutes left, replacement centre Colm O'Shea slipped away from two defenders to score ‘Tarf’s third try – yet the usually reliable Lane, who made the initial break in the lead up to the try, watched his conversion attempt come back off the left hand post.
It was cruel luck on ‘Tarf who showed great resilience to hang in there, but the new champions made certain of their ninth successive league victory in the dying minutes.
Second row Beirne missed out on a try when referee Eddie Hogan O’Connell could not spot the grounded ball under a pile of bodies.
‘Tarf looked to have weathered the storm until Ronaldson ripped the ball free from Matt D’Arcy’s grasp. Lansdowne’s replacement scrum half Marcus Walsh was hauled down close to the line, and fittingly it was Roche who reached out for the line to complete the scoring.
The final whistle sparked jubilant scenes on the all-weather back pitch as Lansdowne celebrated their first top flight success, making it three title winners from Dublin in as many years – Old Belvedere (2011) and St. Mary’s College (2012) were the most recent champions.
Referee: Eddie Hogan O'Connell (IRFU)