AN evening of contrasting emotions ended in controversial circumstances when referee George Clancy went to the video referee (TMO) to determine if Leinster's Sean Cronin had scored a match-winning try after he had signalled the end of the game.
The TMO eventually ruled 'no-try' but it was a truly bizarre end to what had been a thoroughly enjoyable contest.
The sight of Ulster captain Johann Muller celebrating a first Ulster inter-provincial win in Dublin since 1999 while the Leinster players and referee awaited the TMO's verdict will live long in the memory.
"He actually said 'ball held up, end of the game'. I celebrated and then suddenly I heard 'TMO'. I don't know what the rules are," explained a bemused Muller after the game.
Ulster coach Mark Anscombe was no more enlightened – "we're still not sure if we've won the game!" – but he was in no doubt that Clancy got it horribly wrong.
"He has a chance to go upstairs but not after he blows the whistle for full-time. And he called full-time. I don't make the rules."
The measure of the challenge mounted by Ulster was reflected in their position at the final whistle, a superiority they thoroughly deserved. Indeed, it was Ulster who played all the attacking rugby in the contest and they will now look forward to their European adventure next weekend with renewed confidence.
Leinster invested all of their considerable energy once more in a match of much drama but found Ulster's organisation and defensive balance a match for their best efforts, not least in those final frantic seconds when their defensive mettle was tested by wave after wave of Leinster assaults.
It was their stoicism in defence and, it must be acknowledged, their innovation with ball in hand that swung this tie in Ulster's favour. But it would be an injustice to Leinster to suggest they cannot seek solace from their efforts.
They contributed handsomely to the contest and had a hard edge, not least in the scrum, something coach Joe Schmidt was keen to pounce on in the aftermath of the defeat.
"I thought we scrummed really well right from the start of the game," said Schmidt. "I know there were a couple that they got the push on from a decent angle, but once we straightened them up I thought we scrummed really well. That's a good starting point."
Schmidt was, however, rather scathing in his criticism of the officiating, especially at the end when the Leinster scrum laid siege to the Ulster line but were frustrated as the set-piece had to be reset a number of times before the final whistle sounded following Cronin's near miss.
"We conceded a penalty-try from the first scrum that went down at Ravenhill. I'm not sure how many went down out there tonight. To say we are frustrated is an understatement," he added.
Schmidt's frustrations are understandable and the risk is they will live to lament the opportunities they lost in the final 20-minute spell when they threatened finally to breach Ulster's formidable defence but came up short.
Their performance was punctuated by some hugely exciting play, not least a magnificent restart from Ian Madigan to Isa Nacewa after Robbie Diack had crossed their try-line to reduce the arrears to 6-5.
It was an innovation of beauty as the out-half measured the kick to perfection. One can only guess at the frustration that Schmidt and the players must have felt when the promising move was undone by the concession of a scrum that afforded Ulster the opportunity to regroup and repel the onslaught.
But despite the obvious strength of the Ulster defence, the sheer weight of Leinster's attacks were such that they yielded Madigan the chance to enhance his reputation and the out-half was only too willing as he kicked three penalties to add to his early brace to open a 15-8 lead eight minutes into the second half.
As the half progressed chances were created at both ends, however, and Ulster could lay claim to creating the more worthwhile opportunities.
Eventually, Ulster took the lead just past the hour mark as second-half replacement Iain Henderson showed all his nimbleness to touch down in the corner after a particularly impressive break by Andrew Trimble.
Madigan and Ruan Pienaar – who did all of Ulster's kicking – swapped further penalties to leave four between the sides with 20 minutes to play.
From this juncture it was all Leinster as they bombarded the Ulster defence but they were undone by their own decision-making, going left from a ruck after 77 minutes when they had a three-man overlap and easy run-in on the right flank. That was just one of the opportunities spurned.
It was symptomatic of a team who simply haven't played together with any regularity for a number of months and they will benefit from the outing, although the loss will probably cost them the chance of a home semi-final in the competition.
Next weekend's assignment is of more immediate concern. Leinster face Wasps in the Amlin Challenge Cup on Friday – "a six-day turnaround is going to be tough," said Schmidt – while Ulster take on Saracens on Saturday evening in the Heineken Cup.
The truth is that Ulster's long-awaited success in Dublin is enough to suggest that they are the Irish side best placed to enjoy next weekend's London invasion.
LEINSTER – R Kearney; D Kearney, B Macken (A Conway 36), A Goodman, I Nacewa; I Madigan, I Boss (J Cooney 74); C Healy, R Strauss (S Cronin 57), M Ross (J Hagan 65); Q Roux (L Cullen 52), D Toner; K McLaughlin (R Ruddock 65), S Jennings, J Heaslip.
ULSTER – J Payne; A Trimble (P Nelson 72), D Cave, S Olding, C Gilroy; P Jackson, R Pienaar; T Court (C Black 71), R Best, R Lutton (K McCall 70); J Muller, D Tuohy; R Diack, C Henry (R Wilson 63), N Williams (I Henderson 56).
Ref – G Clancy (IRFU)