Leigh Halfpenny’s 13-point kicking haul proved Leinster’s undoing at Parc y Scarlets tonight, but three converted tries still earned the reigning Guinness PRO14 champions a valuable losing bonus point.

Converted tries from wingers Fergus McFadden and James Lowe cancelled out an early Ken Owens effort, which came while Josh Murphy was in the sin-bin, as Leo Cullen’s men went off at half-time leading 14-10 and with Scarlets prop Samson Lee in the bin.

Halfpenny landed two more penalties to nudge the Llanelli outfit in front and Gareth Davies’ opportunist 68th-minute try pushed the margin out to nine points. Captain Rhys Ruddock touched down with five minutes remaining to set up a grandstand finish, but the Scarlets hung on to open their win account for the new season.

A typically breathless start between these sides saw the Scarlets threaten first, clever work on the left wing launching Hadleigh Parkes deep into Leinster territory. The visitors leaked a couple of penalties in scoring range and young flanker Murphy paid the price with a fifth-minute yellow card.

Turning down the place-kick, the Scarlets emerged scoreless due to Leinster forcing a knock-on. The hosts’ next attack sprung centre Parkes through a gap again but a superb cover tackle from Ross Byrne denied Gareth Davies a certain try, leading to a knock-on over the line and a five-metre scrum for the province.

The pressure kept coming from the Welsh region, though, and their skipper Owens burrowed over from close range despite the best efforts of Ruddock and Tadhg Furlong right on the whitewash. With TMO confirmation of the score, influential full-back Halfpenny converted from the left to make it a full seven-pointer.

Murphy returned just after Byrne was narrowly wide with his first penalty attempt of the night, awarded after Steven Cummins had infringed at a lineout. Leinster missed out on what would have been a cracking try in the 18th minute, as Jordan Larmour and Lowe linked brilliantly on a kick return but the former’s pass to Rory O’Loughlin was ruled forward.

However, there was no denying McFadden in the 24th minute, the winger collecting O’Loughlin’s long pass, expertly stepping inside Parkes’ challenge and finishing with aplomb in between two other defenders. The score originated from a monster 20-metre maul by the pack, and Byrne nailed the conversion from out wide to bring Leinster level.

Toner and captain Ruddock were getting through a huge amount of work in defence, yet a high tackle from the latter allowed Halfpenny to kick the Scarlets back in front from a central 35th-minute penalty. Nonetheless, Leinster dominated the closing stages of the first half as the home side gave away a series of penalties.

Tighthead Lee saw yellow for collapsing a maul right on the Scarlets’ try-line, from which Sean Cronin was adjudged to have knocked on in the act of scoring. With rain now falling, Leinster had a further maul and scrum before quick passes from Jamison Gibson-Park and Byrne sent Lowe diving over in the left corner. Byrne nailed the difficult conversion for a four-point lead at the break.

The Scarlets had the better of the early exchanges in the the second period, Halfpenny’s 50th-minute penalty punishing a scrum infringement by Furlong. A break by Gibson-Park, followed by a strong carry from Cian Healy, set up a shot in response for Byrne but he pulled his kick to the left and wide.

Fortune favoured Dan Jones with some of his line kicking, one strike from a penalty on halfway giving the Scarlets pack a gilt-edged maul opportunity. Halfpenny then clipped over his third successful penalty following an O’Loughlin offside, and a James Davies penalty win, close to his posts, thwarted Leinster’s attempts to respond.

In a crucial passage of play Leinster lost possession in their 22, handing the Scarlets quick ball on the counter and good feet from Parkes and scrum half Davies opened up the defence for the latter to score. Halfpenny’s reliable right boot made it 23-14, leaving Leinster with it all to do.

Peter Dooley got over a breakdown ball to win a momentum-building penalty, and with fellow replacement Joe Tomane getting over the gain-line soon after, Leinster powered through for Ruddock to scramble over for his try from a close-in ruck. However, Byrne’s conversion proved to be the final scoring act as despite good yardage gained by McFadden and Larmour out wide, Leinster were unable to manufacture a match-winning score.