Having scraped past tournament debutants Exeter Chiefs at the RDS in Round 1, Leinster needed a strong start at the Parc y Scarlets and they got exactly that as they raced into an 11-0 lead after 19 minutes.

Jonny Sexton's second-minute penalty was followed by an Isa Nacewa try just six minutes later as the Fijian wing caught his fly-half's accurate cross kick before holding off George North's challenge to touch down in the left-hand corner.

Sexton was off target with the difficult extras but Leinster remained in control and deservedly stretched their advantage when the Ireland playmaker struck another three pointer just before the game hit the 20-minute mark.

Leinster still led by 11 at the break and that lead became even more substantial three minutes after the interval as Sexton punished Rhys Priestland for a second penalty miss with a superb long-range drop goal.

The Scarlets faced a uphill struggle to force their way back into the contest against a side chasing a third successive Heineken Cup title but they did give themselves real hope thanks to a 10-point tally in just seven minutes.

First, Priestland finally got the hosts on the board with a penalty on 47 minutes and then Gareth Maule scored a fine try, which Priestland converted, to cut the gap to four points with 26 minutes still to play.

Maule stood up Leinster legend Brian O'Driscoll on his way to a fine individual score but the Scarlets failed to created another try-scoring chance of note in the closing stages.

Instead it was Leinster who edged further clear with two more Sexton penalties, although a solitary reply from Priestland while Ian Madigan was in the sin bin late on did at least salvage a losing bonus point for the Scarlets.