Isa Nacewa crossed for the only try of the game,as Leinster narrowly defeated the Cardiff Blues, in turgid conditions at Cardiff Arms Park.
The first half was a less than impressive performance, due to the abysmal conditions, and the sides were locked level until the dying embers of the first half. Ian Madigan – who was making his 140th appearance for the province - slotted a late penalty which saw Leinster lead 6-3 at the break.
Leinster had a chance to further extend their lead when Fergus McFadden latched onto the end of a Madigan cross-field kick, but the Blues scrambled well, and Rhys Patchell showed great composure to usher the Leinster winger.
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Things went from bad to worse for McFadden, as he was subsequently binned for a dangerous tackle on Lloyd Williams.
However, due to the gale force winds, the Blues were reluctant to kick, so opted to keep the ball in hand. They continually rallied at the Leinster defence, who showed great character despite being a man down.
Early in the second half, the Blues attacking efforts were rewarded as they levelled up the scores. Neither side could craft an opening until Jack Conan slipped down the blindside of a maul before handing Nacewa an easy finish.
Leinster held out in defence, blocking a valiant drop-goal from Patchell. The win saw Leinster leapfrog Ulster into second place, only two points behind leaders Connacht with a game in hand.
It should be business as usual for Leinster, who face a trip to strugglers Zebre, who received an eight-try beating at the RDS only two weeks ago. Cardiff, host fourth-placed, Ulster, who will be looking to return to winning ways following a defeat to Scarlets.