Missed penaltypublished at 62 mins
Leinster 20-10 Northampton
Are the cracks starting to appear?
Ross Byrne misses a shot at goal and the chance to stretch the lead.
Summary
Four-time winners Leinster through to Champions Cup final on 25 May
Leinster will face Toulouse or Harlequins at Tottenham Hotspur Stadium
James Lowe scored two tries as Leinster dominated first half
Lowe completed hat-trick in second half before visitors fought back
George Hendy and Tom Seabrook set up grandstand finish but hosts held on
Record 82,300 fans at sold-out Croke Park in Dublin
Missed penaltypublished at 62 mins
Postpublished at 19:03 British Summer Time 4 May
Leinster 20-10 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports ExtraWhat a ball that was from Alex Moon the second row. Worthy of an international full-back the way he caught the ball and passed it.
I thought George Hendy had made a mistake with the chip but James Lowe couldn't cover it.
Converted Try - Leinster 20-10 Northamptonpublished at 58 mins
George Hendy (con Fin Smith)
Lifeline for Northampton.
The ball goes through the hands and George Hendy kicks forward.
It looks like possession would be lost again but Leinster fail to claim it and Hendy capitalises to score.
Fin Smith adds a good conversion.
Image source, PA MediaPostpublished at 56 mins
Leinster 20-3 Northampton
Chance gone.
Northampton have a scrum deep inside Leinster territory but the hosts launch into the set-piece and win the penalty.
Leinster can clear their lines.
'It's not far off men against boys'published at 18:57 British Summer Time 4 May
Leinster 20-3 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports ExtraIt's wave upon wave of Leinster attacks. They are dominating collisions and then moving the ball at pace into space to someone in a better position.
Flip that around and Northampton haven't dominated any collisions or managed to get the ball away at pace.
It's not far off men against boys.
Image source, Getty ImagesPostpublished at 54 mins
Leinster 20-3 Northampton
George Furbank tackles opposite number Ciaran Frawley into touch to stem the Leinster attack.
Saints have actually defended reasonably well against the onslaught by the Irish side, but they have struggled to land a shot in attack.
Postpublished at 51 mins
Leinster 20-3 Northampton
Now then.
Saints tuck the ball up the jumper and charge at the Leinster line.
But as the blue shirts start to smell an opportunity at the breakdown, the noise reverberates around Croke Park.
The ball is lost and Leinster win the penalty.
Image source, Getty ImagesPostpublished at 48 mins
Leinster 20-3 Northampton
Tommy Freeman carries Northampton over the gainline but the support is not forthcoming and the visitors lose momentum.
Leinster are continuing to dominate at Croke Park.
'Magnificent galloping charge'published at 18:47 British Summer Time 4 May
Leinster 20-3 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports ExtraThat was a magnificent galloping charge by Ryan Baird, showing unbelievable speed and athleticism for a big player.
Then there were two or three brilliant offloads to deliver the ball to Lowe for a walk-in try.
Image source, Getty ImagesTry - Leinster 20-3 Northamptonpublished at 43 mins
James Lowe
That's the hat-trick.
Ryan Baird makes the initial break before the ball is eventually moved wide for James Lowe to claim his third try of the game.
He becomes the first man to score a hat-trick in a Champions Cup semi-final.
Ross Byrne misses the conversion.
Image source, Getty ImagesPostpublished at 42 mins
Leinster 15-3 Northampton
Alex Mitchell does well to cling on to Ryan Baird, with only the try line behind him.
Leinster knocking on the door again...
Kick-offpublished at 40 mins
Leinster 15-3 Northampton
Ross Byrne gets us back up and running...
Postpublished at 18:39 British Summer Time 4 May
HT: Leinster 15-3 Northampton
How do Saints turn this around?
They probably have to retain possession better. They gave the ball away too cheaply in the first half.
Story of the halfpublished at 18:34 British Summer Time 4 May
HT: Leinster 15-3 Northampton
James Lowe has done the damage in a couple of key moments, but a word for Jamison-Gibson Park's quick-thinking for both tries...
Image source, Getty Images
Image source, Getty ImagesPostpublished at 18:30 British Summer Time 4 May
HT: Leinster 15-3 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports ExtraIt's been a story of Leinster dominance off the back of Northampton mistakes. Northampton were loose and nervous but Leinster piled into them and showed the ruthless instincts of champions.
Image source, Getty ImagesHalf-time - Leinster 15-3 Northamptonpublished at 18:26 British Summer Time 4 May
Josh van der Flier knocks on after several phases of Leinster attack.
Fin Smith decides enough is enough for the first half and picks up the loose ball to kick it into touch.
Postpublished at 18:25 British Summer Time 4 May
Leinster 15-3 Northampton
Chris Jones
BBC rugby union correspondent on BBC Radio 5 Sports ExtraWhat an opportunity for Saints! They beat the blitz with slick passing but it was overrun and the try went begging.
Penalty - Leinster 15-3 Northamptonpublished at 39 mins
Fin Smith
Northampton are on the board after a neat Fin Smith penalty.
Postpublished at 38 mins
Leinster 15-0 Northampton
Terrific hands by Saints opens the Leinster door by James Ramm has to take the ball behind him and then loses control.
We'll come back for the penalty and Fin Smith will have a shot at goal.
Image source, ReutersPostpublished at 35 mins
Leinster 15-0 Northampton
Fin Smith clips the ball through the Leinster defence but James Lowe is on hand to clear up and fire the ball into touch.