From Tottenham Hotspur Stadium - Southampton produced a stunning late surge to come from behind and beat Tottenham 3-2 thanks to two goals in three second half minutes in north London.
The Saints started strongly and should have gone ahead inside the opening five minutes when Mohamed Elyounoussi picked out Che Adams with a pearler of a cross, but the striker could only shoot straight at Hugo Lloris from close range.
After Cristian Romero had a goal disallowed for offside, the home side went close again when Harry Kane slid in Sergio Reguilon, but the Spaniard was denied as Fraser Forster made himself big to stop the net bulging.
Spurs began to take control and soon took the lead as Jan Bednarek diverted Pierre-Emile Hojbjerg's cross beyond Forster.
However, that advantage was quickly wiped out courtesy of some shocking Tottenham defending. Davinson Sanchez and Ben Davies both failed to clear their lines and the ball eventually found its way to Romain Perraud, who squared for Armando Broja to tap in.
Boos greeted the Tottenham players at half-time as Southampton pinned the hosts in, with Lloris making a string of saves to take the two teams into the interval locked at 1-1.
Antonio Conte introduced new signings Rodrigo Bentancur and Dejan Kulusevski from the bench in a bid to earn Spurs all three points, but just before the Swede came on, Tottenham finally put a phase of decent football together which culminated in Lucas Moura crossing for Son to make it 2-1.
Spurs were poor for large periods - making unforced errors at a rather astonishing rate - and they should have been pegged back when Broja ran through from nothing, but the Albanian could only blaze over.
However, the Saints made an incredible late charge to take a 3-2 lead, scoring two identical goals. Mohamed Elyounoussi headed in James Ward-Prowse's excellent cross to level it up before the England midfield bagged another assist, teeing up Che Adams to give the visitors the lead.
Substitute Steven Bergwijn thought he'd nicked Spurs a point in injury time, but the Dutchman had strayed too far and had his strike chalked off by VAR.
Tottenham player ratings
1. Goalkeeper & defenders
Hugo Lloris (GK) - 8/10 - Terrific save in the first five minutes to deny Adams from close range. Had already made four top-class stops by the half-hour mark. Kept Spurs in it during a match in which they were outplayed for large periods.
Davinson Sanchez (CB) - 2/10 - Prodded the ball aimlessly into his own box when he should have cleared before Broja struck. Got caught out twice by long balls when he shouldn't have. Clumsy challenge by the touchline saw him booked. In no man's land for Southampton's second and third goals.
Cristian Romero (CB) - 7/10 - Had a goal disallowed for offside. Great pass over the top led to the first goal. Was the most proactive of Tottenham's defenders with Sanchez and Davies performing horrendously alongside him.
Ben Davies (CB) - 4/10 - Looked like he'd slipped on a banana when trying to clear in the build-up to Southampton's leveller. Pretty poor all in all.
2. Wing backs & midfielders
Emerson Royal (RWB) - 2/10 - Had a real torrid time, struggling to keep up with both Perraud and Elyounoussi. Lack of pace was seriously exposed. Nowhere to be seen as Elyounoussi and Adams ghosted past him to score their headers.
Harry Winks (CM) - 4/10 - Couldn't provide any stability in midfield as his direct opponents swarmed. Got better with Bentancur's introduction but played it backwards and safe far too often.
Pierre-Emile Hojbjerg (CM) - 3/10 - Put the cross in which Bednarek converted. Booted the ball aimlessly upfield a few times, much to the disgust of the Tottenham supporters.
Sergio Reguilon (LWB) - 6/10 - Missed a golden opportunity to open the scoring, shooting straight at Forster with the goal at his mercy. Good outlet down the left.
Lucas Moura (RW) - 6/10 - Pretty anonymous first half and sent a half-chance wide at the start of the second. Good ball across goal set up Son to make it 2-1.
Harry Kane (ST) - 7/10 - Great ball across goal which Reguilon should have converted. Dropped deeper in the second half and picked some excellent passes to get Spurs moving. Headed a Reguilon cross into the ground and over the bar.
Son Heung-min (LW) - 7/10 - Nearly grabbed the first goal but it was instead turned into his own net by Bednarek. Didn't get too many opportunities but kept his cool to put in Lucas' cross.
Rodrigo Bentancur (CM) - 7/10 - Came on for Hojbjerg. Immediately gave a more calming and progressive presence on the ball.
Dejan Kulusevski (RW) - 5/10 - Few nice touches but ran the ball into touch a few times.
Steven Bergwijn (ST) - 5/10 - Introduced late on and nudged in what Spurs thought was the equaliser, but he was offside.
Southampton player ratings
5. Goalkeeper & defenders
Fraser Forster (GK) - 5/10 - Strangely, his side dominated the shooting statistics and he wasn't needed all that often. Couldn't get close to either goal.
Kyle Walker-Peters (RB) - 6/10 - A largely hopeful punt upfield actually turned into a decent ball for Broja. Got a warm reception as a former Spurs defender.
Jan Bednarek (CB) - 5/10 - Got his positioning wrong and poked past his own goalkeeper for the opener. Wicked delivery put Southampton's second goal on a plate for Elyounoussi.
Mohammed Salisu (CB) - 7/10 - Showed good speed and awareness to cut out a few Spurs attacks. Good and proactive.
Romain Perraud (LB) - 8/10 - Good awareness to pick out Broja for the equaliser. Smacked the bar with a fierce drive from range. Got booked.
6. Wing backs & midfielders
Stuart Armstrong (RM) - 6/10 - Saw a header clawed away by Lloris. Also shot just wide from range. Covered a lot of ground.
James Ward-Prowse (CM) - 9/10 - Excellent set-piece delivery, as is to be expected. Bagged two assists with some trademark crosses which won Southampton the game.
Oriol Romeu (CM) - 7/10 - Helped Southampton win the midfield battle in the first half, snapping into challenges - though he did give away a few fouls in the process. Booked for a cynical challenge on Son.
Mohamed Elyounoussi (LM) - 9/10 - Awesome ball in set up a glorious opening for Adams who spurned it. Gave Emerson all sorts of problems with some excellent runs. Came off his wing to net the Saints' second equaliser with a great header.
Che Adams (ST) - 7/10 - Should have tapped in from Elyounoussi's brilliant cross. Did get his goal later on, nodding in Ward-Prowse's cross for the winner.
Armando Broja (ST) - 7/10 - Got on the end of Perraud's cross to finish well for the equaliser. Great chance to take the lead but he screwed a shot horribly wide. Was dispossessed a little too frequently throughout.
Shane Long (ST) - /10 - Introduced as Southampton ran down the clock late on.
Ibrahima Diallo (CM) - N/A - See above.
Theo Walcott (ST) - N/A - See. Above.