Cullen’s side did find their second try on 32 minutes, fighting their way into the 22 before Doris flicked the ball on to Van der Flier, who broke Jeremy Sinzelle’s tackle on his way to the line.
Leinster were then hit with a triple blow, with Porter sin-binned for a high tackle on Mikheil Shioshvili, Seta Tuicuvu able to score in the corner as Toulon piled the pressure on and Byrne yellow carded for offside.
With the score 14-11, Leinster withstood pressure before half-time and delivered the game’s crucial passage of play after the break.
Still down to 13 men, the Dublin-based province shifted the momentum against the odds, forcing a sin-bin for Teddy Baubigny for a high tackle and sending Ringrose over for their third try from the next play.
Byrne kicked another penalty to stretch the lead to 22-11 and with the hosts on top at the scrum they looked to put the game out of reach for their visitors.
It was not a classic semi-final of high quality. Byrne missed another kick at the sticks before the tireless Doris got what would prove to be the decisive try on 66 minutes.
Three minutes later Toulon finally found their edge, Serin and Drean’s tries threatening the unlikeliest of comebacks.
It was not to be for the three-time winners but they will take some comfort in a first semi-final in the competition since they last won it in 2015.
“We had match point,” said a frustrated Mignoni, Toulon’s director of rugby.
“But unfortunately we dropped the ball. That’s how it is, that’s elite sport, that’s life, that’s rugby.
“Not many people thought we could win here. We weren’t far off but now we have to work to get back into the Champions Cup next season.”
For a team with the history of Leinster eight years is a long time without a title, they will hope the resolve shown in seeing out this win can carry them to a fifth star on the shirt.
