Chelsea were stunned by a Harry Kane-inspired Tottenham to surrender their lead at the top of the Premier League.
Diego Costa's tap-in put Chelsea ahead, but Kane's low shot levelled before Danny Rose followed up a rebound.
Kane was tripped by Gary Cahill for an Andros Townsend penalty, with Kane's turn and shot giving Spurs a fourth.
Eden Hazard's run gave Chelsea hope, but Nacer Chadli's deflected effort ensured John Terry's late goal from close range was only a consolation.
The Terry goal does, however, mean Chelsea are equal with Manchester City in terms of points, goal difference and goals scored, so the pair are officially classed as joint-top of the table.
If that situation remains at the end of the season, they would play-off for the title.
That Jose Mourinho's side have relinquished top spot is only one aspect of a result made especially notable for the manner in which Spurs dismantled a team they had failed to beat in their previous 10 attempts.
On 22 November, Chelsea had an eight-point advantage over City, only to lose two and draw two of their next eight games.
Chelsea began the new year at the top of the table - a position they have occupied on each of the three previous occasions they have won the Premier League - but they have been joined by a City side that have taken 22 points from a possible 24.
Meanwhile, Spurs go fifth by extending their unbeaten run to six games and by becoming only the second team to ever score five goals past a team managed by Mourinho.
They turned around the scoreline after Costa's opener by employing Chelsea's method of attacking with runners around a central spearhead.
Spurs made the better start but were behind when Hazard's mazy run ended in a shot against the post, with Oscar firing the loose ball back towards Costa, who had the simple task of turning it in.
From there, Chelsea looked set to dominate - Cesc Fabregas provided the service for Costa to run into the channels with support arriving from Hazard and Oscar - and they could have perhaps have been given a penalty when Jan Vertonghen handled as he fell in the box.
But, Kane, with the help of the excellent Chadli, first reversed the momentum then pulled Spurs out of sight in the space of 22 minutes either side of half-time.
Out of nothing, Kane cut in from the left, evaded three challenges and fired in along the ground from outside the penalty area.
Then, when Cesar Azpilicueta was dispossessed on the halfway line, Christian Eriksen fed Chadli, who hit the post before Rose followed up.
With Chelsea rattled, Cahill was sluggish as he caught Kane in the box, allowing Townsend to make it 3-1 at the break.
When Kane neatly turned Nemanja Matic to finish inside the far post, Spurs looked capable of handing out a humiliation.
Hazard stopped the rot with a low finish after a one-two with Oscar, but any suggestion of a Chelsea fightback was snuffed out when Chadli deservedly got on the scoresheet after being played in by Kane.
Terry rounded off a hugely entertaining game when faced with an empty net at the far post, a goal to complete the only scoreline that could have left Chelsea and City level at the top.
Credit: BBC
