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' in a truly bizarre end to a thoroughly enjoyable contest.
The sight of Ulster captain Johann Muller celebrating a first Ulster inter-pro win in Dublin since 1999 while Leinster players and referee awaited the TMO 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 in calling for the TMO.
"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 this weekend with renewed confidence.
Leinster invested all 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.
"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.
The final 20 minutes 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.
The focus now switches to next weekend's assignments.
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 at Twickenham.
The truth is that Ulster's long-awaited success in Dublin is enough to suggest that they are the Irish province best placed to enjoy next weekend's London invasion.