Dele Alli's pair of headers inspired Tottenham to victory over Chelsea, ending the Blues' 13-game winning run.
The England international opened the scoring in first half stoppage time as he rose highest to head home Christian Eriksen's cross.
And the second, which came 10 minutes after the break, was a carbon copy as the forward guided the ball home with his head to send Spurs 2-0 up and they saw out the game from there.
Below are five things to take away from the game.
Chelsea never seemed to chase the points here
After a tempestuous start died down, the order of things was clear: Spurs played high, Chelsea sat back.
It was a risky gambit, and one that over-relied on a counter attack – which seemed to misfire all too often once gained.
It a sort of caginess we have come not to expect of Antonio Conte's Chelsea: showing a lack of ambition, while on a run of 13 wins.
With a trip to Liverpool coming up at the end of the month, Conte will need to reconsider the value of this particular game plan.
We saw the bad old Costa
Yes, he was kicked left right and centre, but this was not a vintage evening for Diego Costa.
The spat he unleashed on Pedro, following a misunderstanding in counter attack, was exactly what you don't expect to see from two members of a top-of-the-league side.
He then bad naturedly rushed a throw-in, never a striker's job, as if to spite the incoming Marcos Alonso.
Petty in-fighting, and negativity – we thought we'd seen the last of this fro Costa.
Chelsea showed schoolboy errors – not once, but twice
To concede one angled Christian Eriksen ball / Dele Alli header combination may be considered unfortunate.
To concede two is no less than careless.
The second goal was almost a carbon copy of the first – and the sight of defenders being out-jumped so easily, albeit by a player who is at the top of his game, will not have pleased Antonio Conte.
Basic training ground stuff that.
The changes frustrated once more
Conte knows what he likes, and he likes to stick to that.
But when things aren't working, people expect changes.
He knows his squad better than anyone, but it was unfathomable here how Cesc Fabregas and Willian didn't get more game time.
Nobody complains about the subs when the team wins, but when it shows as little as was offered here throughout – those questions are justified in being raised.
Don't panic
Quiet contentment is not a state known to many football fans, but remember this: Chelsea remain five points clear at the top of the league.
This was expected to be the toughest game for this particular stretch – one of the toughest of the season – and Chelsea have made hay while the sun shined, in preparation for this.
Dropping these three points, particularly in a London derby, will hurt.
But it gives Conte an opportunity to look at what went wrong, and to build upon that.
He keeps on telling us how much his Chelsea need to 'work and work', and how they will improve if they do.
Time to deliver on that...
