Replacement fly-half Ciaran Frawley kicked three crucial penalties, including a stunning effort from deep in his own half, to help a determined Leinster Rugby overcome Investec Champions Cup holders Stade Rochelais.
The visitors had lost both of the past two finals to their hosts, who were greeted by a rapturous home support at the Stade Marcel Deflandre.
The crowd played their part in a tight first half, both teams having players sent to the sin bin at the same time following an overblow of tension, with second row Joe McCarthy and centre Jonathan Danty the players punished.
Almost immediately after, Jordan Lamour went over in the corner amidst boos and whistles for the only try of the game – fly-half Harry Byrne converting.
Stade Rochelais were restricted to just two penalties in the opening 40 by a committed Leinster Rugby defence, fly-half Antoine Hastoy kicking both either side of Lamour’s try.
A late penalty from Frawley, who had quite literally just come on for the injured Byrne, sent Leinster Rugby in 10-6 to the good but knowing they would need to give it their all for the second period.
That they did, with their defence holding up against Stade Rochelais’ incessant attack. It was a heroic display from the Irish province, who only let Stade Rochelais pick up three more points from Hastoy’s third penalty.
He missed a crucial chance to add another three, while Frawley made no such errors as he kicked his second penalty.
But his best came right at the death, with an audacious attempt from inside his own half. His effort was really meant to run down the clock, but as it turned red the ball sailed between the posts to stun the home supporters and finally give Leinster Rugby a win over Stade Rochelais.
Leinster Rugby will now face Sale Sharks in Dublin, while Stade Rochelais must travel to DHL Stormers.