Arsenal blew the chance to go top of the Barclays Premier League as Tottenham fought back from 2-0 down to triumph 3-2 and record a remarkable first victory at the Emirates Stadium.
Samir Nasri and Marouane Chamakh had put the Gunners in complete control as they looked set to leapfrog Chelsea, but Spurs - who had just one Premier League away victory over their old rivals, in May 1993 - regrouped for the second half following the introduction of fit-again England striker Jermain Defoe.
Gareth Bale pulled a goal back on 50 minutes, before an inexplicable handball from captain Cesc Fabregas from a free-kick gave away a penalty, which Rafael van der Vaart converted.
Arsenal were then condemned to successive home league defeats for the first time in 13 years when Younes Kaboul headed in a dramatic late winner.
After hauling themselves level, Spurs turned the game on its head with five minutes to go when Van der Vaart floated a free-kick into the penalty area, where Kaboul got between his markers to guide the ball into the far corner.
There were five minutes of stoppage time, during which Arsenal pressed, but Spurs were not to be denied a famous win.