Llanelli - 51 Leinster - 20 The celebrations have barely finished, yet Leinster's Six Nations heroes discovered the frailty of their new-found stardom after being humbled by Llanelli.
Just three weeks after seven of this Leinster side clinched a historic Triple Crown victory over Scotland, they were brought crashing to earth at Stradey Park.
Replacement John McWeeney grabbed two tries in the final five minutes, but by then the Scarlets had crossed six times, scoring four tries in a blistering 20-minute spell in the second half, to punish a lethargic Leinster.
The victory means Llanelli take maximum points to keep up the pressure on Ulster at the top of the Celtic League, while the size of the defeat should serve as a serious jolt to Leinster's stars.
Llanelli were in desperate need of a boost to lift the gloom that has hung over Stradey Park since their Heineken Cup exit against Biarritz last week and were determined to avoid a second defeat in seven days that could dent their hopes of another title.
So it was inevitable that in front of an expectant crowd they should make the livelier start, despite the late withdrawal of number eight and talisman Scott Quinnell through injury.
Wales outhalf Stephen Jones, top scorer in the Six Nations, slotted over two penalties in the opening 20 minutes, both for offside, after Chris Wyatt and then Salesi Finau had been held up over the line.
By that time Leinster's international brigade had cleared their heads and begun to string together the phases that eventually brought about their opening try, through Horgan, before half an hour.
Ben Gissing crashed through the midfield, after Victor Costello's lineout take, and could possibly have scored had he stretched for the line.
Possession was instead recycled for Felipe Contepomi, who offloaded to Horgan for the simplest of tries.
Yet having gained ground with ease, through Costello and wing Brendan Burke, Leinster switched off with the same suddenness with which they had got going.
They fell asleep at a lineout, allowing Simon Easterby a free run, and Dwayne Peel darted around the back of a ruck and over in the corner to give Llanelli a 13-5 lead at the break.
Jones and Contepomi exchanged penalties before Llanelli launched their rout.
Easterby's break and Mark Taylor's over-the-shoulder pass sent Garan Evans sailing over before Peel, Barry Davies and even prop John Thiel ran Leinster ragged.
McWeeney's arrival gave Leinster the urgency they had lacked but by the 75th minute it was far too late.
LLANELLI: B Davies; G Evans, M Taylor, T Selley, S Finau; S Jones, D Peel; I Thomas, A Gravelle, J Thiel, A Jones, C Wyatt, S Easterby (capt), D Hodges, I Boobyer. Replacements: R McBryde for Gravelle (half-time), M Phillips for Peel (68 mins), R Rees for Finau (74 mins), E Lewis for Boobyer (77 mins). Tries: D Peel (2), B Davies (2), G Evans, J Thiel. Cons: S Jones (6). Pens: S Jones (3).
LEINSTER: G Dempsey; S Horgan (D Quinlan, 75), B O'Driscoll, G D'Arcy, B Burke; F Contepomi, B O'Riordan; R Corrigan (capt), S Byrne, P Coyle, M O'Kelly, B Gissing, V Costello, D Dillon, N Ronan. Replacements: A McCullen for Ronan, E Byrne for Coyle (55 mins), B O'Meara for O'Riordan (65 mins), J McWeeney for Burke (67 mins), L Cullen for Gissing (68 mins), G Hickie for S Byrne (71 mins). Tries: J McWeeney (2), S Horgan. Con: F Contepomi. Pen: F Contepomi.
Referee: M Changeleng (Scotland).
