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
Leinster 15-0 Northampton
Courtney Lawes shows all of his class.
Wave after wave of Leinster attack finally thwarted by the long levers of the former England forward.
Great work at the breakdown by Lawes and a momentary reprieve for Saints.
Leinster 15-0 Northampton
Chris Jones
BBC rugby union correspondent on BBC Radio 5 Sports Extra
The Leinster machine is working like clockwork.
Northampton have not had a sniff.
Leinster 15-0 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports Extra
There have been a lot of errors from Northampton but being caught offside chasing the kick-off is as bad as it gets.
Leinster 15-0 Northampton
Schoolboy from Northampton.
The green and black shirts are metres in front of Fin Smith from the restart and Leinster will have the scrum on halfway.
Ross Byrne
Ross Byrne won't miss from there.
Leinster win a penalty in front of the posts and decide to take a simple three points to stretch their lead beyond two converted tries.
Leinster 12-0 Northampton
The blue flags are flying high...
Image source, PA MediaLeinster 12-0 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports Extra
In front of 82,000 people and away from home against an immensely capable Leinster team, you hope your players can rise to the occasion but there have been a litany of mistakes from Northampton players.
Leinster 12-0 Northampton
Saints enjoy a couple of phases in possession before Josh van der Flier is quickly in at the breakdown to turn over.
It's difficult to stop a world-class operator from there.
Leinster 12-0 Northampton
Chris Jones
BBC rugby union correspondent on BBC Radio 5 Sports Extra
It's like Northampton are playing with a bar of soap the way they are handling the ball.
Leinster 12-0 Northampton
A moment to savour and a moment to forget in 25 seconds for Juarno Augustus.
The number eight wallops James Lowe with a thumping hit, but then loses the ball two phases later with Saints in possession.
Image source, Getty ImagesLeinster 12-0 Northampton
The first quarter of the game is behind us and Leinster have made 90 metres compared to Northampton's 13.
One-sided.
Leinster 12-0 Northampton
Quick hands free James Ramm on the wing but he is unable to throw the pass back inside.
It's another unforced error by Saints, who are struggling to gain a foothold in the game so far.
Leinster 12-0 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports Extra
Disaster for the Saints. They were in control of the ball but the pass was well read and in the panic they gave the penalty away and Leinster made them pay.
James Lowe
James Lowe at the double.
Leinster drive towards the Saints line with a rolling maul, which is brought down just short.
The ball is popped out and Jamison Gibson-Park bats it onto Lowe once more for another finish in the corner.
Ross Byrne misses the conversion this time but Leinster are firing.
Image source, Getty ImagesLeinster 7-0 Northampton
Saints are in danger of being blown away here.
Ross Byrne makes the break after intercepting a loose pass and the noise is deafening.
Leinster 7-0 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports Extra
Keep your eyes open! Gibson-Park will go from anywhere and launched a Hail Mary pass over the heads of the Northampton players.
That is the worst possible start and Northampton can't complain because they have been complicit in what happened.
James Lowe (con R Byrne)
First blood to Leinster.
They have the penalty five metres out and Jamison Gibson-Park reacts quickest with a fast tap before flinging the ball wide for James Lowe.
The wing catches and beats the covering defence to get over for the opening try.
Ross Byrne adds the conversion.
Image source, Getty ImagesLeinster 0-0 Northampton
Paul Grayson
Former Northampton and England fly-half on BBC Radio 5 Sports Extra
In the pressure-cooker atmosphere Northampton are in, giving away the ball cheaply is going to hurt them.
Image source, Getty ImagesLeinster 0-0 Northampton
Man-mountain Courtney Lawes shares a word and a smile with diminutive Leinster scrum-half Jamison Gibson-Park.
It follows a Saints knock on from a pre-rehearsed move and it's been a bit of a nervy start by both sides.
Leinster 0-0 Northampton
James Lowe gets his hands on the ball out wide and the Ireland wing takes a couple of Saints defenders with him.
The ball is recycled into midfield but it is spilt forward.
Solid defence so far by the visitors.