Leinster stretched their lead at the head of the table to a dozen points in the BKT United Rugby Championship at Parc Y Scarlets on Friday night.

They made it seven straight wins from five tries by Chris Cosgrave, Rob Russell, Thomas Clarkson and back-to-back penalty tries to take the bonus-point away from West Wales.

Straight from the first lineout, Ross Molony’s delivery off the top and the disguised pass from Charlie Ngatai were the main moments in giving Cosgrave the chance to cut through for his first try on his second start, converted by Ross Byrne in the third minute.

When Scarlets earned the rights to a lineout inside the 22, Leinster held the line before giving up a penalty for offside, inviting a second throw and a series of drives which Dave Kearney ended by clamping down on the ball.

This fueled Leinster’s next attack as Max Deegan, John McKee and Rhys Ruddock got over the gain line.

Deegan swiped a Scarlets lineout to initiate a sustained period of pressure in which Molony lost the ball close to the line and, shortly after, almost released Cosgrave with an offload.

The swing in play brought the home crowd to life when Jonathan Davies’ left-handed pass put Stef Davies outside Kearney to make it 7-5 in the 21st minute.

Still, Leinster were patient in how they took the ball up, moving it to the wings Rob Russell and Kearney in pursuit of width.

Russell’s grubber was energetically chased by McKee, the ball coming off the diving hooker’s head for Russell to ground for his third try of the season, Byrne converting for 14-3 in the 27th minute.

Deegan dented Jonathan Davies in the tackle and the Irish province looked in control until the class of Gareth and Jonathan Davies threatened to eat into the lead.

It took the footwork of Ross Byrne and support from Ed Byrne to keep Leinster in charge as well as Deegan’s low, hard tackle into winger Tom Rogers to bring the half to a close.

Deegan nabbed his second steal against the throw. Charlie Ngatai’s composure took Leinster out of trouble. Prop Byrne and hooker McKee combined to stifle Dan Jones.

Out-half Byrne was calm under a high ball and Leinster’s collective cohesion in contact forced Scarlets to retreat.

Then, the lineout delivered again through Molony, triggering a barrage of carries for tight-head  Clarkson to claim his first try on his 20th cap, Byrne adding the extras for 21-3 in the 49th minute.

Ross Byrne ghosted through the line to apply further pressure. Deegan popped up on the left to make headway.

But, when the play broke down, Johnny McNicholl’s behind-the-back wonder pass sent Ryan Conbeer up the left and Cosgrave had to use all his speed to beat Stef Evans to the ball at the posts.

Leinster were keen to stack up the fourth try, turning down two shots at goals to pick up the bonus-point when McNicholl joined Dan Jones in the bin for a deliberate knock-on, producing a penalty try on the hour as Scarlets were reduced to thirteen.

Even then, Leinster had to repel two lineouts, Molony acrobatically snatching the second, and survive without Michael Milne, yellow-carded for an accumulation of team indiscretions.

Ross Byrne was nimble in clutching an interception and firing a fine left-handed pass for Leinster to move away again.

Then, Charlie Tector was summoned forth for his debut just as the Leinster maul rumbled forward for another penalty try in the 73rd minute, Gareth Davies binned for his part in the process.