Tries from Shane Horgan and Stephen Keogh drove Leinster to a 17-point win over the Cardiff Blues at the RDS, moving the European champions back to the top of the Magners League in the process.

Cardiff place-kicker Ben Blair had an off night with the boot, kicking only two out of five penalty attempts, while Leinster out-half Jonathan Sexton booted 13 points to help his side to a deserved victory.

Coming off the back of a great derby win over the Ospreys last week, the understrength Blues could not cope with a strong Leinster outfit whose stellar back-line provided a constant threat.

The opening try came when Luke Fitzgerald blitzed the Cardiff defence and Sexton's sublime grubber kick gave winger Horgan a relatively easy pick-and-run for the line.

In the opening half, the majority of Cardiff's chances came from the boot of Blair, but kicking into a strong breeze, the New Zealander was only able to convert two out of four penalties.

After a comfortable start to the first half, things suddenly started going wrong for Leinster.

Number eight Jamie Heaslip was sin-binned in the 34th minute for killing the ball and two minutes later Blair scored Cardiff's second penalty after Sean O'Brien was penalised for holding on.

Then, in the 39th minute, Leinster were dealt an injury blow as Gordon D'Arcy had to make way for Girvan Dempsey with what appeared to be a hamstring problem.

The best opportunity for the Blues to cross the Leinster try-line came on the stroke of half-time but Blair, with a clear run to the line, was unable to hold onto the final pass.

Three minutes into the second half, Blair had the chance to reduce Leinster's 13-6 lead but his effort crept wide of the posts.

Ten minutes later, Sexton put further daylight between the teams as his sweetly-struck penalty just cleared the bar.

Michael Cheika's men started to exert their dominance in the final quarter as they threatened the Cardiff whitewash repeatedly.

But they had to be patient as their second try did not arrive until the 77th minute when replacement Stephen Keogh broke through a tackle and finished off well.

Cardiff's experienced centre Gareth Thomas almost got a consolation try in the dying moments when he had a clear run to the line, but Fitzgerald got back quickly to close him down.