Leinster completed a historic Guinness PRO14 and Champions Cup double with a free-flowing 40-32 final victory over the Scarlets at the Aviva Stadium.

Leo Cullen’s side ran in five tries and man-of-the-match Jonathan Sexton kicked 13 points as they became the first Celtic team to win the domestic and European Cup titles in the same season, a feat their 2011 and 2012 predecessors failed to achieve.

Leigh Halfpenny booted the Scarlets into an early 6-3 lead and Johnny McNicholl’s well-taken try cancelled out a Devin Toner effort, but James Lowe’s deftly-finished score on the stroke of half-time had Leinster 21-11 to the good.

The increasingly-influential Sexton stepped up as captain after a calf injury, unfortunately, ended Isa Nacewa’s 185th and final Leinster appearance in the 18th minute, while the Scarlets also lost Aaron Shingler to a knee injury.

The Conference B table-toppers put the game beyond the Scarlets’ reach with third quarter tries from Sean Cronin and Jordan Larmour (with another one for the highlight reel), coupled with a further score from Jack Conan. Time ran out on the defending champions’ late comeback, although the classy McNicholl finished with a hat-trick and replacement prop Werner Kruger also crossed late on.

Wayne Pivac’s charges were much improved compared to last month’s 38-16 Champions Cup semi-final defeat to the same opposition, and an early poach from James Davies offered encouragement. Yet, Sexton gave Leinster a sixth-minute lead from the tee.

Scarlets full-back Halfpenny, who shrugged off a hamstring injury to start, responded with two penalties by the 12-minute mark, rewarding flanker Shingler’s restart work and punishing a James Ryan offside.

Rob Kearney raised the decibel level among the PRO14 final-record 46,092 crowd by beating Halfpenny to a Sexton garryowen, the latter turning forward pressure into three points, but Nacewa had to come off soon after. His replacement Rory O’Loughlin broke through a gap in the lead up to Sexton’s third successful kick, which crept over via the right-hand post.

Leinster finally made their 80% share of possession count on the half-hour mark, number 8 Conan launching a prolonged attack from deep via a scrum. Lowe and Tadhg Furlong also had key involvements before lock Toner was driven over for an unconverted 29th-minute try.

The Scarlets soon found joy in the outside channels, moving the ball at pace for Steff Evans and Gareth Davies to go close and set up winger McNicholl to snipe over in the 34th minute. Halfpenny failed to convert at 14-11 and with the interval approaching, Leinster showed their champion quality. Twice they kicked for the corner before soft hands from Luke McGrath and Sexton sent Lowe diving over on the short side. Sexton’s conversion wormed its way over for a 10-point split at the break.

Despite the Scarlets defending Leinster’s first attacking wave on the resumption, Sexton found a superb touch after Scott Williams’ high tackle on the Ireland out-half, and hooker Cronin duly sprung over in the right corner from the resulting maul.

Sexton bent his touchline conversion through the uprights for a 28-11 advantage, and young gun Larmour’s chasing down of his own kick and terrific pick-up served up the province’s fourth try. The margin was suddenly out to 22 points.

The Scarlets worked the ball wide for McNicholl to acrobatically touch down in the 64th minute, Halfpenny’s well-struck conversion giving them some hope at 33-18 down, but Conan brilliantly slammed the door shut four minutes later, replacement Joey Carbery’s slick footwork taking him past Hadleigh Parkes before the supporting McGrath sent Conan in under the posts for a thunderous team score.

Carbery’s conversion had Leinster counting down the minutes to their first PRO14 title success since 2014 and a record fifth in all, yet the Scarlets deserve plenty of credit for their finish, Kruger muscling over from close range and McNicholl adding an injury-time seven-pointer, created by centre Williams’ barnstorming run.

Giving his reaction afterwards, Leinster head coach Cullen said: “The European final in Bilbao a couple of weeks ago, the feeling at the end was incredible. Because it was so tight and only going into the lead in the 79th minute of the game. The last couple of weeks have been a mental and physical test for all of us.

“Huge challenge last week against Munster in the RDS and dealing with the celebrations etc, etc. To try and get our feet back on the ground this week was a challenge, but credit the players. They’re the ones that produce the goods on the field and I thought they were exceptional.

“Seeing this guy beside me (Isa) lift the trophy at the end is probably the thing that gives me the most satisfaction. I feel a little bit like an irresponsible parent the fact that he was out there in the first place but it was hard to deny him, watching him in the last couple of weeks.

“He stepped up to kick the penalties two weeks ago (against Racing), but to see him lift the trophy again there today, nobody deserves it more. Nobody deserves it more, I am delighted for him.”

Nacewa admitted: “I said I wanted to come back and win trophies and coming back with Johnny at the same time, from his little time away (with Racing). We were in a bit of an evolution to get to the point today, with 55 players used in this campaign and the Champions Cup, and the way we used the whole squad.

“It took longer than expected but the timing’s right, the coaches have been phenomenal in the way they’ve managed the group and managed the players. We learnt a lot from last year, so it wasn’t hard to come back here.

“I blew my calf quite early (in the game). It’s not the way I envisaged it but Locko (Rory O’Loughlin) had trained well all week and he was outstanding when he came on, a massive impact again. A good day.”

Join next season’s epic adventure with a 2018/19 Leinster Rugby Season Ticket.

Leinster Rugby Season Tickets