Relief for the Scarlets as Sean Cronin goes in too high on John Barclay.

The Welsh region get a maul rolling off the line-out, but Gareth Davies punts a box kick straight into the air and it falls probably less than a metre further forward than where he put boot to ball.

Not ideal.

Relentless from Leinster.

Jordan Larmour twists, skips, hops his way beyond a flurry of red defenders as the blue machine keeps rolling forward, only to be stopped by John Barclay narrowly short of the Scarlets line.

Leinster scrum on the five-metre line. Robbie Henshaw hits the line at speed on the inside, and Scarlets' scrambling defence just about keeps him out.

Wave after wave of blue drive is repelled, before Leigh Halfpenny somehow comes out with the ball and flicks it to Hadleigh Parkes beyond his own line.

It's a panicky boot clear.

Drop-out for Scarlets after a Leinster boot trickles long. But the hosts pick up where they left off with a spell of pressure, aided by Rhys Patchell's inability to hold a high ball.

Jordan Larmour makes chase from Jamison Gibson-Park's deft chip, and Steff Evans is forced over his own line.

Leinster get the second half started.

Right then, what can Scarlets do to turn this around? Some of that free-flowing, attacking rugby we've become used to wouldn't go amiss...

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

Leinster were a ruthless machine in that first 40, a brutal mix of power and panache.

The Scarlets need a second-half miracle.

The winners of this one will face Racing 92 or Munster in the final in Bilbao on Saturday, 12 May.

Legendary All Blacks fly-half Dan Carter starts on the bench for the French side in that one tomorrow, but caught up with the guys from BBC's Rugby Union Weekly before the semi-final stage.

Feast on this for some half-time enjoyment...

Dafydd Pritchard
BBC Sport Wales at the Aviva Stadium

It must be rather demoralising playing against a team as unerringly accurate and ruthlessly efficient as Leinster.

That was near perfect rugby and, after such a chastening 40 minutes in this cauldron of atmosphere, Scarlets might be relieved only to be trailing by 15.

Dafydd James
Former Lions and Wales back on BBC Radio Wales

Leinster are sharper in every facet of the game. Their quick breakdown ball is causing so many problems for the Scarlets. Leinster are using their power play to suck the Scarlets in and then moving the ball wide.

The first 10 minutes of the second half are crucial to the Scarlets' chances but you have to say it looks like a one-way track.

And that's the break.

At the moment, Leinster look to be steamrollering their way to Bilbao.

Scarlets have 40 minutes to turn this semi-final around.

Good scrum from Scarlets. They can stick it deep into Leinster territory and work from there.

Hadleigh Parkes hits the line at speed following the line-out, Dan Jones flicks a pass on to John Barclay and now Scarlets go left.

Aaron Shingler is the man in the channel, but he can't collect and the attack fizzles out.

Rare error from the hosts as Cian Healy lets a simple pass slip inside the Scarlets half.

I think that's Rob Kearney getting some treatment and it gives both sides a quick breather.

Scarlets remain within touching distance via the accuracy of Leigh Halfpenny's boot.

Good pressure from Scarlets.

The hosts look to go through the middle and then fling it wide, earning a penalty.

Scarlets captain Ken Owens attempts to take matters into his own hands with a chest-pumping carry. This is the first time we've seen Scarlets actually get some ball in hand.

They're stopped illegally by the hosts, and Dan Jones sticks the penalty 22 metres from the Leinster line.

Quick, decisive ball from the Welsh region, But John Barclay is felled and the home defenders have time to recover.

Dafydd James
Former Lions and Wales back on BBC Radio Wales

It was only a matter of time as sustained pressure finally took its toll. Scarlets are in a bit of disarray - they haven't really been in this game for the first 27 minutes and it's Leinster's consistent power game that is dominating.

Robbie Henshaw is hitting the Scarlets line like he's been fired out of a cannon.

The hosts work it left, before Johnny Sexton sends a diagonal kick towards the chasing Fergus McFadden - the winger's pressure forces Gareth Davies over his own line and the hosts get the put-in.