Replacementpublished at 69 mins
Saracens 24-15 Northampton
A number of subs to update.
Elliot Daly, Duncan Taylor and Eroni Mawi are on for Saracens. Alex Goode, Nick Tompkins and Mako Vunipola have departed.
FT: Saracens 38-15 Northampton
Saracens play Sale or Leicester at Twickenham on 27 May
Maitland scores twice for Sarries, Van Zyl and Malins also score plus penalty try
Mitchell and Ramm gave Northampton hope in second half before Sarries eased clear
Saracens finished top of the Premiership table, Northampton fourth
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Adam Lanigan
Saracens 24-15 Northampton
A number of subs to update.
Elliot Daly, Duncan Taylor and Eroni Mawi are on for Saracens. Alex Goode, Nick Tompkins and Mako Vunipola have departed.
Saracens 24-15 Northampton
Lovejoy Chawatama
London Irish prop on BBC Radio London
Saracens look tired now. They look more tired compared to Northampton.
Northampton are used to long periods of ball in play but they also have nothing to lose now.
It's all on Saracens and Saints can go and enjoy their game. That can make things easier.
James Ramm
How about this?
Northampton show us the offensive rugby that they have demonstrated all season.
They finally put the defence on the back foot and it is worked along the line with Courtney Lawes supplying Australian wing James Ramm and he finishes it brilliantly.
But Fin Smith cannot make the conversion. That could be huge as the gap is nine points.
Saracens 24-10 Northampton
We are now into the final quarter and that Alex Mitchell score means that Northampton are just about in touch.
But they still need two converted tries to draw level.
Saracens 24-10 Northampton
Saracens have just coughed up a certain try!
All Max Malins has to do is pick the ball up and dive over but the ball slips through his hands and he knocks on.
That would have been game over.
Saracens 24-10 Northampton
Paul Grayson
Former England fly-half on BBC Radio 5 Live Sports Extra
Northampton needed that. Saracens defended so well but it was the brilliance of Alex Mitchell breaking from the base.
He breaks all the rules, runs sideways across the field, a show and go, gets through the gap, a nice little break and goes under the posts.
Northampton needed something, they found it from their scrum-half. They need to throw caution to the wind as they are two scores behind.
Alex Mitchell, con Fin Smith
A glimmer of hope for Northampton!
Brilliant work from scrum-half Alex Mitchell as he takes it upon himself to provide the spark.
He holds off a tackle from Jackson Wray and then his dancing feet sell the dummy to opposite number Ivan van Zyl and he then touches down.
Fin Smith then adds the extras.
Saracens 24-3 Northampton
Northampton have had more of the ball in this half, but they have not done anything to the scoreline this half.
Saracens have so far shown why they finished top of the table after 20 games.
Saracens 24-3 Northampton
Northampton have now completely changed their front row.
Robbie Smith and Paul Hill are on for Tom Cruse and Trevor Davison.
While for Saracens, Nick Isiekwe has failed his HIA and will not continue. Callum Hunter-Hill will stay on for the rest of the game.
Saracens 24-3 Northampton
Lawrence Dallaglio has described the Saracens defence on TV as a "black wall".
That is very apt as Northampton cannot find any gaps in it as they go through the phases but find no way through.
Saracens 24-3 Northampton
Saracens and England forward Nick Isiekwe is down after appearing to be hit in the head by Northampton wing Tommy Freeman in a tackle.
He is off for a head injury assessment.
Saracens 24-3 Northampton
Lennie Newman
Former Northampton Saints player and manager on BBC Radio Northampton
This takes a bit of the sting out of Northampton. The seeds of doubt are put in their mind again.
Owen Farrell
And from the resulting penalty, Owen Farrell opts to take the three points on offer.
Good game management from the home team as the gap is now three converted tries.
Saracens 21-3 Northampton
A magnificent tackle from Ivan van Zyl as he nails fly-half Fin Smith and Jackson Wray completes the turnover.
Saracens are not giving Saints an inch here. This is awesome stuff.
Saracens 21-3 Northampton
Northampton enjoy a good spell of possession but they cannot pierce the Saracens defensive line.
It ends with the ball being turned over again. Another big tick for the Sarries defensive coach!
Saracens 21-3 Northampton
A change in the front row for Northampton.
Alex Waller has been replaced by his younger brother, Ethan.
Saracens 21-3 Northampton
The players are back on the field.
More of the same from Saracens? Or have Northampton got something special up their sleeve?
#bbcrugby
Greg Rose: Farrell showing all first half why England struggle defensively without him.
Saracens 21-3 Northampton
We are at the halfway point of the first semi-final with Saracens looking a good bet to make the Twickenham final on 27 May.
Tomorrow it's the second semi-final as Sale Sharks host Leicester Tigers (KO: 15:00 BST).
AJ Bell Stadium is sold out on what promises to be a huge afternoon for Sale and rugby in the north west.
One of their local boys, Raffi Quirke, told BBC about growing up in a football-mad area to make it with the 15-man game.
HT: Saracens 21-3 Northampton
Lennie Newman
Former Northampton Saints player and manager on BBC Radio Northampton
Northampton's game plan is to get sides wide and all they have done is play very narrow, very straight, very physical, and it's not working.
You often find when a team's back is against the wall they revert to the game plan they should be playing.
Credit where credit is due, Saracens have been clinical and at their brilliant best. It's not that Saints have been poor.