But Ignacio Mieres missed an injury-time penalty as Exeter came close to grabbing a deserved draw at the RDS.

Argentina fly-half Mieres had the chance to hand Rob Baxter's Aviva Premiership outfit a share of the spoils with the final kick of a hard-fought and well-matched contest. But Mieres missed to the right of the posts as Leinster breathed a sigh of relief.

Sexton fired the home side, aiming to win their third successive crown in Europe's premier competition, ahead with a close-range penalty on 11 minutes.

But Exeter showed little fear and, although No10 Gareth Steenson missed two kickable penalties to tie things up, the fly-half did level the scores on the stroke of half-time.

Sexton put Leinster back in front with a second penalty in the 54th minute, but Steenson responded with 15 minutes remaining.

However, Sexton added a third successful effort with seven minutes left on the clock as Exeter replacement Ben Moon was penalized for an infringement before Mieres' miss from 49 metres.