The Blues' record run of 17 successive home wins was ended as Leinster's superior finishing skills saw them secure what could prove to be a vital five points in the context of the title race.

Young backs Luke Fitzgerald (2) and Jonathan Sexton both touched down for the second week running, while number eight Jamie Heaslip also crossed the whitewash for a buoyant Leinster side.

Cardiff remain top of the table courtesy of table but this was a reality check for Dai Young's men who failed to capitalise when Leinster had two players sin-binned in the second half.

Young called it a "kick in the backside" and things did not go the way of the Blues from the off. Early on, centre Dafydd Hewitt was held up over the try line after a break from fly-half Nick Robinson looked like creating a certain try.

A high tackle from Xavier Rush on Trevor Hogan allowed Sexton boot Leinster into an eleventh-minute lead from all of 48 metres.

The visitors really built the foundations for this success on a rock-solid defence and good covering saw Blues winger Tom James knocked into touch close to the whitewash.

Leinster moved 8-0 in front as the opening quarter came to a close. Robinson and Ben Blair failed to deal with a kick launched their way, handing Leinster a scrum 15 metres out from the hosts' line.

Short drives from Bernard Jackman and Stan Wright sucked the Cardiff defence in and a long cut out pass from Christian Warner sent winger Fitzgerald scurrying over in the right corner.

Sexton missed the conversion and the response from the Blues was immediate. Robinson launched a penalty through the uprights from 45 metres out and a superb side-stepping run from Blair led to flanker Mark Lewis going over out wide to level the score.

But a Sexton penalty kick, again from distance, which nudged in off the post handed Leinster an 11-8 lead at the break, with Robinson missing an injury-time chance to reply.

The Blues really should have been in front at that stage as Jamie Roberts, the joint-top try scorer in this season's league, agonisingly knocked on in the act of scoring late in the first half.

The second period opened with Leinster showing more control up front. From a decent position on the hosts' 22, Sexton pinged a kick to the corner which Fitzgerald snapped up for his second try.

Sexton added the extras but a brace of penalties from Robinson after 53 and 56 minutes all but erased that try. Cardiff's hopes of coming from behind were aided a minute later when Leinster had debutant centre Fergus McFadden sin-binned for killing the ball.

Yet the yellow card seemingly inspired Michael Cheika's side as they made the most of their try-scoring chances to move 30-14 ahead by the 66th-minute. Heaslip dotted down after hooker Bernard Jackman had claimed an intercept and run 50 yards to tee up ruck ball which Leinster quickly turned into their third try.

Sexton missed the conversion but the Ireland 'A' international was on hand five minutes later to dart over for the bonus point-clinching score which he converted himself.

By the time Leinster had prop Wright yellow carded, with four minutes of normal time remaining, the result was as good as confirmed, and a try for James in injury-time was only a consolation for the Cardiff as Leinster, on a night when flanker Keith Gleeson made his 100th appearance for the province, scored a memorable win.