LEINSTER SURVIVED a late scare to reach their third Champions Cup final in a row.
Cian Healy made a record 111th appearance in the competition, in front of its highest attendance of 82,300.
And James Lowe lit up the occasion with a hat-trick of tries but Leinster saw a 20-3 lead whittled down to just three points with five minutes to go.
But, between them, Jack Conan and captain Caelan Doris secured a vital penalty with 40 seconds left to play to book their place in the May 25 decider at the Tottenham Hotspur Stadium.
They will face either Toulouse or Harlequins who meet in the other semi-final on Sunday afternoon.
Coach Leo Cullen – who played in the only other rugby game played at Croke Park, in 2009 – said: “It was an amazing occasion and we are very appreciative of the support we’ve had.
“They certainly got 80 minutes of entertainment, maybe a bit too much excitement at the end.
“Credit to not just the Leinster players but to Northampton who fought to the end. We dug in and we’re delighted to get to another final.
“When the score goes to 20-3 early in the second half, the human nature part of that is you try to sit and protect that lead and it’s a real challenge to manage that and maybe we struggled a little bit.
“There are plenty of learnings in that, some of our players have not played for the last while, whether that had an impact I don’t know.
“We will need to try and play a better game in the final.
“Toulouse have been the standard-bearers in this competition. You go back to the start and they were the ones out of the blocks in terms of professionalism.
“They were light years ahead of us and it feels like we’ve been chasing them ever since.
“And Quins, we’ve quite a bit of history with them in this competition as well. They’re fresh in mind because we watched them against Northampton last week and they’re similar in that they’ve got a really strong attacking intent.
“It’s a final isn’t it? It’s on the day and we’ve to make sure we’re the best version of ourselves.”