Leinster's wait for a fifth Champions Cup title goes on after a remarkable final in Dublin where they lost a 17-point lead and were reduced to 13 players at the end of an incredible battle against Ronan O'Gara's La Rochelle.
For the third year running, it was the French side, under the stewardship of former Ireland and Munster out-half O'Gara, who denied Leo Cullen's favourites.
The defending champions scored the winning try with seven minutes to play and although Leinster had a late period of pressure, La Rochelle escaped when Michael Ala'alatoa was red-carded for a dangerous clear-out on the line.
Leinster's season ends in bitter disappointment once more and the departures of captain Johnny Sexton and senior coach Stuart Lancaster only serve to heighten the sense of regret.
They made a blistering start and rampaged into a 17-0 lead with tries from Dan Sheehan (2) and Jimmy O'Brien but Stade Rochelais scored two of their own to gain a foothold.
The first-half effort took a savage toll on the home side and when their discipline and kicking skills departed in the second half, La Rochelle sensed the game was there for the taking, and so it proved.
Leinster, beaten finalists in 2019 and 2022, kicked just three points in the second half and when out-half Antoine Hastoy converted replacement prop Georges Henri Colombe's try, the French side led for the first time.
A lead they would not relinquish in a game that had echoes of last year's final in which Leinster lost 24-21 in the last play of the game.
If the Heineken Champions Cup did perfect starts, then this was it.
Not in his wildest dreams could Leo Cullen and his coaching staff have foreseen what transpired in the opening 12 minutes.
Just 40 seconds were on the match clock when Sheehan touched down for the opener.
Moments before, with Ross Molony proving a convincing dummy in the lineout, the hooker lobbed the ball to Jack Conan, who returned the pass to Sheehan, who had a run-in from 20 yards, with Ross Byrne adding the extras.
Conan beat a couple of defenders from the restart and James Lowe kicked the sweetest of 50:22s.
With clean and fast possession, Lowe and Hugo Keenan made the ground before a perfect long pass from Byrne set up O'Brien to dive for the corner.
When Josh van der Flier won a turnover penalty, Jamison Gibson-Park tapped quickly before being tackled by Tahera Kerr-Barlow.
The scrum-half was sin-binned and Byrne kicked to the corner and after a couple of phases, Gibson-Park found Sheehan loitering on the wing and the 24-year-old dived in for his sixth competition try.
The crowd of 51,711 erupted as Byrne's kick hit the upright again.
La Rochelle had not been in the game but that was soon to change. Playing off a penalty advantage from a scrum close to the line, Jonathan Danty bumped Garry Ringrose before dotting down to give the visitors something to build on with Hastoy converting.
Leinster didn't panic and in a nine-minute spell, O'Gara's side's indiscipline cost them; three penalties for a side entry, not releasing the player and then holding Van der Flier off the ball allowed Byrne to kick six points to give Leinster a 23-7 advantage.
But it came at the cost of a head injury to James Ryan, the captain, who had been outmuscling his bigger forward opponents to this point, departed for Jason Jenkins.
When Leinster failed to deal with an up and under, Paul Boudehent led the chase and was only denied by the covering Keenan.
Stade stayed patient and worked their way into position again and centre UJ Seuteni found the gap after a number of carries had sucked in the Leinster defence.
Hastoy's conversion was the last score of an incredible half of rugby.
The out-half combined with Seuteni at the start of the second half and Leinster conceded a penalty under the posts as they scrambled back.
Tadhg Furlong, who sat out yesterday's captain's run,a couldn't go on, and Ala'alatoa came on for the Ireland prop in the 45th minute.
It was frantic and Byrne restored the nine-point margin with a penalty before Gibson-Park kicked his clearance directly out and Robbie Henshaw, after a super tackle, placed his hands on the ground past the ruck and Hastoy tapped over the penalty.
The Top14 outfit threatened again after Byrne's clearance was blocked but Sheehan came up with a turnover close to the Leinster line and they survived
But they had made 119 tackles to 31 and a fractured kick chase betrayed their fatigue. La Rochelle sensed it, the French commentators in the press box got excited as Lowe screwed two kicks into touch and the visiting hordes raised the decibel level even further.
La Rochelle lead!
— RTÉ Rugby (@RTErugby) May 20, 2023
Georges-Henri Colombe burrows over after some relentless pressure. And Leinster down to 14 as Kelleher is binned
26-27 La Rochelle #LEIvSR
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Van der Flier disrupted a powerful maul; Henshaw came up with a big turnover before retiring with Charlie Ngatai coming on; former Connacht and Ireland lock Ultan Dillane made his way on as Leinster hung on.
Doris went off his feet and La Rochelle turned down the three points to kick to the corner. Leinster continued to infringe and it was only a matter of time before La Rochelle took the lead.
Colombe barged over and it also cost Leinster a man as Rónan Kelleher, who had just replaced Sheehan, was deemed to be at fault. Hastoy again converted to make it 27-26 and the 14 men had eight minutes to rescue their dream.
La Rochelle soon lost the numerical advantage when Danty slammed his shoulder into Doris and joined Kelleher in the bin.
Ngatai almost powered over in the corner before Ringrose lost the ball in contact.
Lowe returned a loose Hastoy kick, Keenan dipped but came up short and Leinster got to within a metre of the line before the play was stopped with Colombe staying down after a ruck.
Referee Jaco Peyper and TMO Tom Foley determined that Ala'alatoa had tucked his arm and made contact with the prop's neck and Leinster's chance was gone and the search for star number five goes on.
Leinster: Hugo Keenan; Jimmy O'Brien, Garry Ringrose, Robbie Henshaw, James Lowe; Ross Byrne, Jamison Gibson-Park; Andrew Porter, Dan Sheehan, Tadhg Furlong; Ross Molony, James Ryan (capt); Caelan Doris, Josh van der Flier, Jack Conan.
Replacements: Rónan Kelleher, Cian Healy, Michael Ala'alatoa, Jason Jenkins, Ryan Baird, Luke McGrath, Ciarán Frawley, Charlie Ngatai.
La Rochelle: Brice Dulin; Dillyn Leyds, UJ Seuteni, Jonathan Danty, Raymond Rhule; Antoine Hastoy, Tawera Kerr-Barlow; Reda Wardi, Pierre Bourgarit, Uini Atonio; Romain Sazy, Will Skelton; Paul Boudehent, Levani Botia, Gregory Alldritt (capt).
Replacements: Quentin Lespiaucq Brettes, Joel Sclavi, Georges Henri Colombe, Thomas Lavault, Remi Bourdeau, Ultan Dillane, Thomas Berjon, Jules Favre.
Referee: Jaco Peyper (SARU)
