Leicester stunned Chelsea at Stamford Bridge as Jamie Vardy’s second-half strike saw Maurizio Sarri’s side defeated at home for the first time this season.
Vardy finished first time in the box from James Maddison’s pass in the 51st minute after the Foxes had withstood heavy pressure.
Chelsea were dominant before the break and struck the bar through Eden Hazard, the best of a host of chances, that came following a Harry Maguire error.
But having gone behind it was Chelsea who became sloppy and Leicester only grew in strength.
Indeed, the Foxes might have doubled their lead but for Cesar Azpilicueta’s sliding block to deny Vardy after Kepa Arrizabalaga had spilled a cross, before the keeper saved well from Marc Albrighton.
Chasing a goal of their own, Chelsea could not break down Leicester’s resistance, despite creating two key late chances.
In the 89th minute, Antonio Rudiger nodded just wide from a corner, before Marcos Alonso struck the post with only the keeper to beat.
The Blues had not lost at home since 1 April, against Tottenham, and this defeat leaves them level on points with fifth-placed Arsenal, who beat Burnley 3-1 earlier on Saturday.
For Leicester, the win moves them up to ninth in the table and is their first victory from 11 matches in London.
Reports before the game spoke not just of pressure on Leicester boss Claude Puel from the club’s owners but of an apparent falling out with his players, too.
There was little sign of the team lacking any motivation or desire on the pitch on Saturday.
Resisting the intensity of Chelsea’s attacking intent is by no means a small feat. Puel’s men not only managed to achieve that, but also to build on it as they forced themselves slowly but surely into the game.
It was Vardy’s goal, scored on his 250th appearance for the club, that sealed victory, but it was a win earned by the whole team through constant running, daring in defence, and precision when it counted.
With Manchester City up next on 26 December, it had been suggested that Leicester’s following match at home to Cardiff on 29 December might even decide the future of their French manager.
Instead, this impressive victory, a first at Stamford Bridge since 2000, must surely now stand as evidence of Puel’s worth.
Chelsea however, will now face questions of their own.