In between times an absorbing and brutal, if at times ugly, first half had played out in Bilbao as Leinster counteracted Iribaren's sniping with a kicking game that targeted their opponents' back three's lack of height.
Three penalties from Sexton had helped Leo Cullen's men keep pace with Racing throughout the game's first 70 minutes, but as it hurtled towards its final stages it was New Zealander Isa Nacewa who made all the difference. On came Remi Tales but at least they could console themselves with Teddy Iribaren kicking them 3-0 ahead.
Leinster won the European Champions Cup for the fourth time by edging Racing 92 15-12 in a dour final at San Mames Stadium on Saturday.
Leinster have never lost a European final and they managed to maintain that proud record with Nacewa's late contribution ensuring that they ended their Champions Cup campaign unbeaten.
Ireland fans will be celebrating in Bilbao tonight. and we hope the same can soon be said of any Irish in Lisbon.
The sides were level 6-6 at the break.
Racing were dealt a blow just before kick-off when All Blacks legend Dan Carter withdrew from the bench with a hamstring injury.
Tristan Thompson breaks silence on life with daughter True
Thompson recently spoke about his daughter for the first time, while appearing on the Road Trippin' podcast on Tuesday. " True is so great but I still can't predict if she is going to sleep the full two hours or if she's hungry".
Starting first-five Pat Lambie sustained a knee injury in the second minute, so French worldwide Tales, who did not feature on the team list in the morning, had to deputise.
The 6-6 scoreline became 9-9 and 12-12 as Iribaren landed four of his five penalty attempts and Sexton finished with three.
From a Leinster line-out, Racing's Leone Nakawara stole possession superbly.
Racing went ahead with an Iribaren penalty but Sexton levelled.
Another offside in front of their posts and Racing were made to pay, Nacewa kicking his second penalty to hand Leinster a 15-12 lead, Tales going wide with an injury-time drop-goal that would have seen added time.
But Sexton responded with a penalty and Iribaren's fourth penalty was cancelled out by Nacewa's boot.