Postpublished at 64 mins
Chelsea's Eden Hazard pulls it back to Marcos Alonso - who loves a shot - and this one from 20 yards is into the arms of Southampton keeper Fraser Forster - his first save of the game.
Summary
Costa heads 50th Premier League goal and then fires in low
Romeu and Bertrand score against former club
Hazard buries from 15 yards, Cahill heads home
Terry makes first league appearance since November
Postpublished at 64 mins
Get involvedpublished at 21:02 British Summer Time 25 April 2017
#bbcfootball
Jasper Shiner: Fraser Forster is without doubt the worst keeper in the Premier League this year.
Harsh?
YELLOW CARDpublished at 60 mins
Oriol Romeu marks his return from a two-game ban by fouling fellow Spaniard Cesc Fabregas. He becomes the first Saints player booked.
get involved Get Involvedpublished at 21:01 British Summer Time 25 April 2017
#bbcfootball
Nikhil: Hazard, Cahill and Costa in my fantasy team, can't get better than that #FPL
#Jealous
And relax....published at 21:00 British Summer Time 25 April 2017
Phil McNulty
BBC Sport chief football writer at Stamford BridgeDiego Costa's header has given Chelsea the vital breathing space they needed and they look locked on course for a seven-point lead at the top of the Premier League.
Stamford Bridge is in buoyant mood and paying tribute to Chelsea manager Antonio Conte.
Image source, ReutersPostpublished at 21:00 British Summer Time 25 April 2017
Cesc Fabregas (103) is now outright second for most Premier League assists, one ahead of Frank Lampard (102), but still well below Ryan Giggs (162).
Image source, PAPostpublished at 58 mins
Southampton were good enough to perhaps edge the first half so we can't rule them out yet and Dusan Tadic forces a good save down low from Thibaut Courtois.
Manolo Gabbiadini then bicyles a shot wide.
Postpublished at 20:58 British Summer Time 25 April 2017
Diego Costa's 50 Premier League goals have come in 85 games - one fewer than Luis Suarez's half-century.
Costa ends goal drought at good timepublished at 20:56 British Summer Time 25 April 2017
Chelsea striker Diego Costa scores his first Blues goal in eight games and surely they are going seven points top. Eden Hazard feeds Cesc Fabregas who crosses for his fellow Spain international to nod home from six yards out.
That's Costa's 50th Premier League goal.
Image source, ReutersGOAL - Chelsea 3-1 Southamptonpublished at 53 mins
Diego Costa
It gets worse for Adams...published at 20:53 British Summer Time 25 April 2017
Granada 0-1 Malaga
Image source, Getty ImagesIt looks like Tony Adams is heading for his third successive league defeat since becoming manager of relegation-doomed Granada - his side are 1-0 down at home to Malaga with about 25 minutes left to play.
The Spanish club are 18th in La Liga and seven points from safety with only four games remaining after tonight's match.
Postpublished at 51 mins
Southampton break but Cedric Soares latches onto a pass that was meant for Sofiane Boufal and the move is over.
YELLOW CARDpublished at 48 mins
Chelsea midfielder Cesc Fabregas slides in and eliminates Oriol Romeu. Definite booking.
KICK-OFFpublished at 46 mins
The second half is under way. Arguably a bigger 45 minutes for Spurs than Southampton.
Image source, EPAget involved Get Involvedpublished at 20:43 British Summer Time 25 April 2017
#bbcfootball
Syed Umar: Don't mind the recent lack of clean sheets. So many goals in recent matches we are very entertaining
Aamer Iqbal: Am I in the minority in hoping Chelsea mess up the title run after they downed tools last season? Not a Spurs fan by the way
Free-scoring Cahillpublished at 20:42 British Summer Time 25 April 2017
That was defender Gary Cahill's seventh goal for Chelsea this season in all competitions.
He also scored for England against Scotland back in November.
Only John Terry (40) has scored more goals in the top-flight than Cahill (26) among current Premier League defenders - excluding penalties.
'Chelsea go through the gears'published at 20:34 British Summer Time 25 April 2017
Chelsea 2-1 Southampton
Pat Nevin
Ex-Chelsea winger on BBC Radio 5 liveWhat a great game of football this is. Very open with two teams attacking all the time. Boufal and Tadic have been superb, the shackles are off at Southampton, they are enjoying themselves.
But Chelsea have a gearbox and they are going through them when they need to.
Image source, AFPRelief around Stamford Bridgepublished at 20:33 British Summer Time 25 April 2017
Phil McNulty
BBC Sport chief football writer at Stamford BridgeChelsea made the perfect start but had failed to capitalise - but Gary Cahill's header has calmed growing anxiety around Stamford Bridge.
How Chelsea needed that because Southampton were growing in confidence the longer that first half went on.
Image source, EPAHALF-TIMEpublished at 20:33 British Summer Time 25 April 2017
Chelsea 2-1 Southampton
That was the last action of the first half, and Chelsea lead at the break.
Chelsea restore lead just before the breakpublished at 20:33 British Summer Time 25 April 2017
On the stroke of half-time Chelsea are ahead again. The corner is played in and half-cleared, but it comes back into the box and Marcos Alonso heads it on.
Diego Costa fancies a wonder-goal and throws himself in for a bicycle kick. But just before it reaches him, Gary Cahill gets his head onto the ball and sends it into the back of the net. Narrowly avoided losing his head there.
Image source, AFP