Leinster placed one hand on the Magners League trophy last night thanks to a score from the most unlikely source. The former Springbok prop Ollie le Roux is far better known for his hard yards, monster tackles and scrummaging prowess than his ability to cross the try line. However, the South African loose-head came up trumps against Llanelli Scarlets in a first half that further confirmed Leinster as the league’s most potent force.

Needing to defeat the Irish province, and with a bonus point to boot, Scarlets finished a distant second as Leinster made it nine successive victories in the competition.

Going into this game, Leinster held a seven-point lead over Munster courtesy of eight successive wins, including key victories over Cardiff Blues and the Ospreys. In contrast, the Scarlets have been less consistent this term than in any other in recent history. Still, theys were keen at least to narrow the gap on the league’s runaway leaders and improve their chance of finishing as Welsh rugby’s leading side in this season’s competition.

That would be scant consolation at the end of a difficult campaign, but the coaching director, Phil Davies, has set his sights on a decent finish.

Leinster, even without Brian O’Driscoll and Gordon D’Arcy in their midfield, began with a purpose and, despite the appalling conditions on a typically blustery night in west Wales, the leaders earned themselves decent field position from which they would have scored had Leo Cullen not have knocked on five metres short. Still, when they forced the Scarlets through 90 degrees at the game’s first scrum four minutes later, a second opportunity arrived. This time it was taken.

Close control around the breakdown enabled Leinster to make the hard yards through Jamie Heaslip, Cullen and Shane Jennings before Le Roux arrived to force his way over. Felipe Contepomi converted for a 7-0 lead.

A penalty from Stephen Jones three minutes later reduced the arrears but such was the Irish domination, at the set piece in particular, that Llanelli struggled for any decent possession.

Rucking and mauling in the mud is a labour of love for the likes of Le Roux and Stan Wright and, as hard as the Scarlets tried, they were simply unable to prevent the visitors from establishing themselves once again.

This time, it was the Scarlets’ scrum that was exposed. When it was penalised for collapsing a scrum, Contepomi restored his side’s seven-point lead with a penalty from 25 metres.

The real hammer blow came two minutes before the break. And this time Wright grabbed the touchdown. Faced with a blanket of scarlet jerseys in front of him, he muscled his way over for a try that was confirmed by television match official Tony Rowlands.

The Scarlets began the second half as Leinster had opened in the first, with ball in hand and with a genuine desire to close the gap.

However, just as Leinster’s work on the front foot had been polished, so their defensive efforts were pretty slick, too. Time and again the Scarlets probed around the short side but on each occasion Leinster hit their targets. Their task was made harder when scrum-half Chris Whitaker was yellow carded for preventing release at a ruck and, with a numerical advantage, the Scarlets once again asserted themselves in the heart of the visitors’ 22. Leinster’s resolve was broken when Dwayne Peel sent in flanker Dafydd Jones for a try that namesake Stephen converted.

The score gave the home support renewed hope and, though the gap still stood at seven points, Llanelli’s resurgence in all areas of the game was beginning to pose problems for Leinster. The visitors were in no mood to let this one slip, though, and three minutes after Jones had put his side back in with a chance, so Malcolm O’Kelly restored order with a carbon copy of Le Roux’s opening try. It was a fitting reward for the lock whose appearance took him past Reggie Corrigan’s Leinster record of 140 caps.

Contepomi converted from close in and, though Whitaker still had seven minutes remaining on his card, Leinster were home if not altogether dry.

A second yellow card, this time for replacement hooker Brian Blaney, caused one or two further problems for the visitors, but they took that setback on the chin and continued to defend with grit and determination.

Star man: Ollie le Roux(Leinster)

Llanelli:M Stoddart (C Thomas 57min); D James, R King, G Evans, M Jones; S Jones, D Peel (capt); P John, M Schwalger (M Rees 40min), B Douglas (B Broster 67min), L Reed, S Macleod, D Jones, G Thomas, A Popham (N Thomas 45min)

Leinster:R Kearney; S Horgan, M Berne (G Dempsey 64min);, F Contepomi, L Fitzgerald; J Sexton, C Whitaker; O le Roux (C Healey 74min), B Jackman (B Blaney 37min), S Wright, L Cullen (capt), M O’Kelly, S Keogh (K Gleeson 50min), S Jennings, J Heaslip

Yellow cards: Leinster:Whitaker 47min, Blaney 52min Try: D Jones 49 Conversion: S Jones Pen: S Jones

Tries: Le Roux 12, Wright 39, O’Kelly 52 Cons: Contempomi 3 Pen: Contepomi

Referee: P Fitzgibbon (IRFU); Att: 7,407