On a wild and windy night in the fortress that has been Ravenhill for the past two seasons, Leinster surprised many with the quality of their performance and there was a strong sense of a team that was growing up in front of one's eyes.
Ulster were rightly proud of not having been beaten at Ravenhill since September 2002, 21 matches ago, and not many of the faithful expected this to be the match that would break that sequence. Certainly, with creaking set-pieces and little continuity, there was little about the Leinster performance last week that suggested the surprise that lay in store.
But, once they recovered from a Des Dillon knock-on off the kick-off, Leinster took the game to their opponents. Playing into a strong wind, Leinster took the lead after some well-worked mauling led to an unconverted try for Ben Gissing after five minutes.
The lead was cut to two when Paddy Wallace converted a penalty before Andrew Maxwell bagged his fourth try in as many matches when getting to a Neil Doak chip first. A fine strike from near the touchline from Wallace extended the lead to 10-5.
Leinster, though, played smart rugby into the wind, keeping it tight but retaining possession well through a muscular and pumped up pack. Ulster's use of the wind through kicking deep was effectively giving possession to Leinster and they worked hard and sensibly in not giving it back. Crucially, Paddy Wallace had an off night with the boot, missing with three first half penalty efforts, including one that was eminently kickable, even in the conditions. This let Leinster off the hook and they survived the loss of the influential Des Dillon to the sinbin for repeated infringement at the breakdown.
Leinster's reward for their first half industry was a try by Christian Warner late in the half which featured a delicious reverse flick from David Quinlan, who took out two players freeing his fellow centre to score in the corner. McAllister stood little chance of nailing the convert into the wind, so the scoreline going into the break was 10-10, with Leinster feeling very good about the state of play.
Two quick penalties by McAllister, including one from his own half, to take the score to 16-10 to Leinster seemed to indicate that the wind would see Leinster through in the second half.
But Ulster began to put some continuity into their own game and got their reward when, after 64 minutes, maxwell stepped well to stretch the wide defence and Bryn Cunningham burst onto Maxwell's inside ball at pace, making it to the line from 40 metres for a superb score and leaving the minimum between the sides at 16-15.
It could have been all over bar the shouting just before that though. As the game opened up, an intercept sent the lively Shane Jennings surging up the line. His offload to James Norton looked certain to result in a try as Norton skipped inside two tackles to touch down. But he had stepped on the line in doing so and was crestfallen when the try was disallowed. 23-10 in the conditions would have signalled the end, but Cunningham's score put the game in the melting pot, with the crowd getting behind the home team.
Leinster held firm though, not least through some superb midfield tackling by David Quinlan, and on 79 minutes added a Brian O'Meara penalty when Tommy Bowe was penalised for not releasing.
Four points was a bit more comfortable, but the icing on Leinster's cake was when replacement scrumhalf Brian O'Riordan dived over from short range deep into injury time to spark the celebrations.
Leinster coach Declan Kidney told leinsterrugby.ie: I'm pretty pleased with the win. We were aggressive in defence and there was a definite improvement in our set-piece.
It was a ding-dong provincial derby with neither side giving an inch and credit must go to all the lads.
It was another brilliant occasion between two sides going hammer and tongs and we're looking forward to what will be another great occasion next weekend.
Leinster: 15: James Norton14: John McWeeney (K. Lewis, 19-26 blood)13: Christian Warner12: David Quinlan11: Gary Brown10: David McAllister (B. O'Riordan, 70)9: Brian O'Meara1: Emmett Byrne2: Gavin Hickie3: Peter Coyle (A. O'Donnell, 60)4: Leo Cullen (Captain)5: Ben Gissing6: Aidan McCullen