A little bit of "anything you can do, I can do better" between Sexton and Halfpenny at the minute.

The Welshman clips his kick over from wide out to bring Scarlets back to within four points of their Irish hosts.

Well, Scarlets need to find an inroad and Fergus McFadden might just have handed it to them, fumbling the kick-off close to his own line.

The visitors' forwards earn a penalty off the scrum. Chance for Leigh Halfpenny to reduce the deficit?

Johnny Sexton pops it over. Leinster extend their lead.

Chris Jones
BBC rugby union commentator at the Aviva Stadium, Dublin

Ireland star Robbie Henshaw has made a near-miraculous recovery from a serious shoulder injury, and he has looked razor sharp for Leinster in the opening quarter.

Dafydd Pritchard
BBC Sport Wales at the Aviva Stadium

This has shades of the first half of Ireland's Six Nations win against Wales at this venue in February, when the hosts dominated early on.

Leinster are pounding the Scarlets' line and, with cries of 'Leinster, Leinster' ringing around the Aviva Stadium at full volume, the home side look in the mood to avenge last season's Pro12 semi-final defeat.

A knock-on from Sean Cronin hands Scarlets a slight breather. It's been a ferocious start from Leinster in the Dublin sun.

Scott Williams attempts a grubber in his own 22 - bravery or madness? - and Leinster collect.

Scarlets' defence is all over the place now and Leinster win a kick-able penalty.

Dafydd James
Former Lions and Wales back on BBC Radio Wales

Leinster have got that juggernaut pack and Scarlets are looking a little bit shaky at the moment.

Henshaw, Sexton, Kearney. It's the Leinster backs causing problems early on. Scarlets look a little caught in the semi-final headlights.

The returning Henshaw bulldozes into a sea of red defenders, Sexton looks to dummy before finding Garry Ringrose and then Tadhg Furlong fancies his chances 10 metres from the line.

The Welsh region have set up camp on their own line.

Dafydd Pritchard
BBC Sport Wales at the Aviva Stadium

Scarlets are renowned for their exhilarating, running rugby but they have started this game in quite a patient, pragmatic manner.

When Leinster are in possession, they don't often surrender it easily, so the Scarlets will have to make the most of it whenever they get the ball.

Rob Kearney watches a high Leinster boot drop out of the sky and gathers well before keeping the ball alive, but the Scarlets turn it over and pop another deep kick into the hosts' territory.

Time for Kearney to recover and pick his spot, and he does superbly - catching the line and trickling into touch.

Leigh Halfpenny is the man tasked with converting the penalty.

Off comes the scrum cap, over goes the ball. Never in doubt.

The Aviva is absolutely rocking with bellowing, hearty Welsh voices.

It takes the visitors a couple of times to get the scrum right, but John Barclay picks up and goes blind before Scarlets usher their way back inside.

Hadliegh Parkes attempts to batter his way through before Steff Evans is caught high.

A chance to stick some points on the board.

The first penalty goes to the hosts. And that gives Leinster a chance to stick it deep into the Scarlets half.

Leinster collect the line-out, but now the Scarlets forwards dig right in and force a turnover of their own.

So much for easing themselves in...

BBC Sport Wales' Dafydd Pritchard is at the Aviva Stadium - you can read his report on the BBC Sport website at the final whistle.

It's a beaut of a day in Dublin, and the travelling Welsh fans are certainly enjoying it.

They're lapping up the atmosphere and a little bit of Ireland's finest stout to boot. Pockets of red are perched around the Aviva, drifting in a sea of bubbling blue home fans.

It's the visitors who get us under way.

Dafydd Pritchard
BBC Sport Wales at the Aviva Stadium

The Scarlets reckon around 10,000 fans have made the journey from west Wales to Dublin - and it sounds like it.

There's no doubt the travelling supporters are outnumbered but they are more than making up for that with some hearty renditions of 'Sosban Fach' and other favourite songs.

Wayne Pivac's men are underdogs today but, having beaten Leinster in last season's Pro12 semi-final at the RDS and then thrashed Munster here in the final, they are quietly confident of causing an upset.

Right, it's almost time for kick-off so let's have a look at the teams...

Leinster: R Kearney; McFadden, Ringrose, Henshaw, Nacewa; Sexton (capt), Gibson-Park; Healy, Cronin, Furlong, Toner, Ryan, Fardy, Leavy, J Murphy.

Replacements: Tracy, J McGrath, Porter, Molony, Conan, McCarthy, Carbery, Larmour.

Scarlets: Patchell; Halfpenny, S Williams, H Parkes, S Evans; D Jones, G Davies, R Evans, Owens (capt), Lee, Beirne, Bulbring, Shingler, J Davies, Barclay.

Replacements: Elias, D Evans, Kruger, Rawlins, Cummins, A Davies, Hughes, Boyde.

Captain Ken Owens is the only player remaining from the last time Scarlets reached the semi-final stage.

Owens was on the bench that day, but is now in line to make his 50th European appearance.

Scarlets have crumbled at this point of the competition in 2000, 2002 and 2007 - could 2018 be their year?

Image source, Getty Images

Scotland captain John Barclay's time in Llanelli is nearing its conclusion after a five-year stint - he joins Edinburgh this summer - and possible European title glory would represent a dream send-off.

The 71 time-capped flanker was pivotal to Scarlets winning the Pro12 last season, which included beating Leinster in Dublin at the penultimate knockout stage.

"It's comfortably the biggest game I've been involved in since I've been at the Scarlets," Barclay said.

"The final of the Pro12 last season was fantastic, but this is Europe and we haven't been in the semi-final for 11 years.

"The guys are just excited about the occasion and what we've achieved. We want to keep the journey going."