Leinster always find a way to win at the RDS against Ulster and they did so again, inspired by Ian Madigan, Ireland's out-half in waiting, who contributed 19 of his team's points, including a smart try from a tap and go penalty just minutes into the second-half.
Joe Schmidt will be as happy as the Leinster fans but there will be some concern as both Jamie Heaslip and Tommy Bowe left the fray early; Heaslip with a stinger to his shoulder while Bowe seemed to be struggling with a leg injury as he departed while he also took a heavy knock to the face.
This was a heavy blow to Ulster, too, now in danger of losing sight of the play-offs and already out of Europe. It had all started so well before the game turned on Dan Tuohy's stupid yellow card just before the break, during which time Leinster won the sin-bin 10-0 to effectively win the game there and then.
Ulster had started the game with decent early territory thanks to two kick turnovers and a lovely linebreak by Dan Tuohy from Paddy Jackson's superb pass threatened the day's first score; on their line, a last-ditch tackle on Franco van der Merwe cleared the danger.
Ulster were given their first opportunity, unsurprisingly gifted to them when Leinster had the ball, Dan Tuohy's tackle on Jack McGrath allowing Darren Cave to poach a penalty effort exactly on half-way.
Springbok Ruan Pienaar smacked his kick off the blue dot on the posts; bullseye in the half-time crossbar challenge but worth nothing here.
He made amends in the 17th minute a few yards further on, when Ian Madigan was guilty of a high challenge on Stuart Olding. Pienaar was winning his battle of wounded knee.
Leinster had barely threatened but did so; a poor kick from Ian Madigan was rescued by Tommy Bowe's inability to gather in his own 22 and Luke Fitzgerald's jinking run ended with a Darren Cave penalty concession.
Madigan's kick was more assured this time and his side were now level as the game ended the second quarter.
He kicked his restart out on the full though and Ulster regained their territorial stranglehold; another Leinster penalty concession beneath the posts gave Pienaar the chance to push his side 6-3 ahead in the 27th minute.
Leinster then lost captain Jamie Heaslip after he shipped a heavy knock on the shoulder during this passage of play; they had already lost the hamstrung Shane Jennings before the kick-off.
Fitzgerald's dancing feet were the only aspect of Leinster's play that were getting the largely subdued crowd near to rising to theirs; another penalty attempt from Madigan levelled matters in the 32nd minute.
They earned a slim, and undeserved half-time lead, when Tuohy was binned for illegally sacking Isaac Boss as he attempted to mine the ball from another desperately slow ruck.
9-6 to Leinster without much rugby played at all, at all.
The sinbinning, which seemed harsh although Tuohy had lost his balance at the time, looked as if it may define a tight game.
Madigan, cleverly tapping a penalty to himself before dotting down beyond two underemployed forwards, assumed the responsibility himself, just as he had done when releasing Jordi Murphy on a flying run down the left just moments earlier.
His conversion blew a hole in the game and Ulster's challenge; 16-9 as many punters were only returning from the bars.
Leinster rarely look comfortable even when peering gift horses in the mouth; after messing up a defensive lineout, Ulster pounded the line and Wiehann Herbst was awarded a try via the TMO to punish the home side's slackness.
It was a boon to the visitors, just as Tuohy returned to even up the numbers; albeit Pienaar's conversion attempt drifted wide for 16-11 in the 52nd minute.
But Leinster didn't take long to re-assert their authority; they were seeing more ball and receiving it quicker too.
More pressure produced another penalty close to the line; Madigan was surely tempted to have another cheeky dart but assistant coach tempered his enthusiasm by racing on to the field with the kicking tee.
Yet just seconds after stretching the lead to 19-11 on the hour, a Devin Toner penalty allowed Pienaar a riposte; his effort was limp, tired and off-target, mirroring his side's efforts as the game entered the final quarter.
It was left to Jack Conan to celebrate his second man of the match award by scoring his team's second try in the final minute.
Leinster: Z Kirchner (J Gopperth 70), F McFadden, L Fitzgerald, G D'Arcy (B Teo'o), D Kearney, I Madigan, I Boss (L McGrath 70); J McGrath (M Bent 73), R Strauss (S Cronin 56), M Ross (T Furlong 56), D Toner, M McCarthy (K Douglas 61), J Conan, J Murphy, J Heaslip capt (J van der Flier 29).
Ulster: P Nelson; T Bowe (L Marshall 49), D Cave, S Olding, C Gilroy, P Jackson, R Pienaar (P Marshall 73); C Black (A Warwick 69), R Best capt (R Herring 75), W Herbst (B Ross 70), D Tuohy, F van der Merwe (A O'Connor 70), R Diack, C Ross (S Reidy (65), R Wilson.
Referee: Marius Mitrea (FIR)
The Sportsground on a wet and windy Atlantic-soaked night can be hell on earth for visiting teams as Munster discovered on New Year's Day. The conditions made for a dramatic backdrop to the perfect evening for Connacht rugby, and let nobody suggest this magnificent win was anything but hugely deserved for the team in green.