Denis Hickie crashed over in the seventh minute of injury time only for Felipe Contepomi to see his conversion rebound off the post with the last kick of the game. The conversion would have levelled the scores and denied the Scarlets a much deserved victory following tries from Matthew Watkins and Barry Davies.
They came after Leinster stunned the Scarlets with a try inside five minutes when Keith Gleeson set Gordon D'Arcy free on half-way and the Ireland centre scampered over under the posts. That sparked a stunning response from the Scarlets who hit back with two tries in four minutes. Watkins out-paced Contepomi's desperate lunge after intercepting D'Arcy's pass to score under the posts.
Moments later, Regan King broke Leinster's lines before Lee Byrne and Mark Jones combined to open space for Davies who darted into the corner. Davies then added a monster penalty from the half-way line before Contepomi responded before half-time to leave the Scarlets 17-10 ahead.
The Scarlets enjoyed the lion's share of the second half but could not find their way past a stubborn Leinster defence. And though Mike Hercus traded penalties with Contepomi, Leinster remained in with a shout right to the end at just seven points behind. The Scarlets had their hearts in their mouths when Hickie, who had replaced Brian O'Driscoll after 63 minutes, went over in the left-hand corner but survived the conversion.