Leinster lost their grip on a potential Heineken Cup home quarter-final after a dramatic defeat to a Northampton side they had pulverised only seven days before.
Jamie Heaslip was the hero and villain as Leinster tried and failed to pull off as dramatic a steal as that compiled by the All Blacks here at the Aviva last month.
With his side trailing in the last minute, his searing break from half-way gave Leinster the chance to earn what would have been the winning score.
However, after 17 further phases his fumble allowed Northampton winger Tom Elliott intercept and streak away for a crushing try in the corner which took away the bonus point from the home team.
Leinster remain top of Pool One and favourites to progress with their destiny in their own hands, but the prospect of them securing a money-spinning home quarter-final could now be much more elusive.
And so Northampton, who a year ago gained revenge in Ulster after humiliation at home, repeated the trick 12 months later as they proved that a week is a long time in sport.
Leinter made too many errors but they did have the opportunity to win this game; they must regroup in January to ensure they don’t cede control of this pool.
“We were bullied last week and we wanted to make sure that didn’t happen again. We focused on the result, not the performance,” said visiting captain Dylan Hartley.
Both sides were forced into late changes, with Sean O’Brien’s dead leg not worth the risk so Shane Jennings, so crucial to the famous 2011 final comeback between these sides, coming in while Kevin McLaughlin stepped in to bench.
For Northampton, Dom Waldouck was also a late withdrawal, meaning that George North switched infield to outside centre while Tom Collins assumed the Welshman’s normal left wing role.
Northampton had vowed to erase their embarrassing reverse on their home patch with an opening physical salvo and they were as good as their word, as they attacked the home side with real intent.
Clearly, they had remembered to pack some passion and desire in their overnight luggage.
After Tom Collins was brushed aside illegally by Rob Kearney after his attempted grubber down the line, the English side spurned the three-pointer and opted for the lineout maul.
After crabbing infield, they punctured a hole in midfield with George North blasting over from close range between Luke Fitzgerald and Ian Madigan.
Steven Myler’s extras made it 7-0 in as many minutes; equalling their entire haul during last weekend’s humiliation.
Leinster regrouped and Ian Madigan’s penalty gave them some footing in a game pockmarked by some thrilling passages of play and a fair few sloppy turnovers.
Northampton kicked to the corner again as they continued to dominate into the second quarter, opting for a lineout maul instead of a three-pointer.
However, as they surged for the line, the TMO denied them a try when they had crossed the line with the ball in Lee Dickson’s hand. Mike Ross’ had saved the try. The away side tried again but Leinster repelled them; trusting their defence as the English side ran out of ideas.
Leinster themselves were a little out of kilter in the ideas department too, passes weren’t sticking and they coughed up two decent attacking scrums in opposition territory.
They should have been 10-3 behind at the interval but Myler horribly hooked a chance wide, much to his rueful chagrin.
Leinster charged at the visitors after the resumption, hammering away at the line after Dickson inexplicably dropped the restart; Madigan’s 46thc minute penalty was scant reward for a whole pile of pressure.
Northampton responded in robust fashion, captain Dylan Hartley twice rejecting kickable penalties in an attempt to maul their way to a second score; twice, Leinster rebuffed their one-dimensional approach.
It was an intense Cup clash, brimming
However, a deft North offload to full-back Ken Pisi almost created a try-scoring chance but the Samoan delayed his pass and Leinster cleared the danger once more as the Saints skewed a subsequent lineout.
However, Leinster’s scrum – with two replacement front-rows on – conceded a penalty in front of the posts and this time Myler made no mistake to push the away side to a 10-6 lead with 15 minutes on the clock.
Back came Leinster once more in this absorbing end-to-end tussle, Madigan narrowing the gap to a minimum. Myler then cocked up another place-kick, albeit from long distance.
But replacement Kohn Fotuali’i nabbed a drop-goal with just 90 seconds remaining to plunge a dagger in Irish hearts.
An even more fatal wound would follow.
Leinster: R Kearney; D Kearney (Kirchner 61), B O'Driscoll, D'Arcy(Gopperth 79), Fitzgerald; Madigan, Reddan; McGrath (Bent 57), Cronin, Ross (Moore 61); Toner, McCarthy Cullen 74); Ruddock (McLaughlin 57), Jennings, Heaslip (capt).
Northampton: K Pisi; Elliott, North, Burrell, Collins; Myler, Dickson (Fotuali'I 54); A Waller (E Waller 71), Hartley capt (Haywood 75), Ma'afu (Mercey 54), Lawes (Dowson 74), Day, Clark, Wood, Manoa (Dickinson 68).
Referee: J Garces (France)