Tottenham suffered their biggest home defeat of Andre Villas-Boas' reign as West Ham ran riot with a stunning second-half display at White Hart Lane.
The Hammers scored three stunning goals in 13 minutes to come away with their first victory at White Hart Lane since 1999.
Winston Reid started the rout with a goal from a corner, Ricardo Vaz Te made doubled the lead and then Ravel Morrison scored a superb solo strike to seal the 3-0 win.
Sam Allardyce had described his West Ham team as "relegation favourites" earlier this week, but on this evidence, the east London side will have no trouble staying up.
Much had been made of West Ham's lack of goals this term because of the absence of Andy Carroll, but the way in which the Hammers took their goals will delight Allardyce, and the visiting fans, who revelled in gaining the bragging rights over one of their arch rivals.
As for Tottenham, the bubble of happiness that came with the arrival of seven new players has now burst. Boos rang out from the home fans at the final whistle. They know there is still much work to do if they are to mount a top-four challenge.
A midweek trip to Russia looked to have taken the sting out of Andre Villas-Boas' side, who lacked a cutting edge throughout.
Despite being underdogs, West Ham had the better of the opening exchanges.
Mohamed Diame sneaked into the Tottenham box, but Jan Vertonghen and Paulinho did just enough to put the midfielder off.
Stewart Downing then whipped in a cross from wide, but Kevin Nolan could only head wide.
Spurs started to get into the game more and Gylfi Sigurdsson slipped Paulinho in to the box, but James Tomkins came to the rescue with a fine tackle.
Spurs were restricted to long shots for most of the opening half hour as Tomkins and Reid performed well to keep Defoe and Christian Eriksen quiet.
Andros Townsend seemed to be the only Tottenham player capable of causing any problems. The winger slalomed past his marker and played a clever ball into Sigurdsson, but Jussi Jaaskelainen saved the forward's low drive.
Townsend could not draw a save out of Jaaskelainen though, as he cracked a 25-yard effort just wide.
Paulinho fluffed two long-range efforts wide, much to Villas-Boas' frustration.
At the other end Reid wasted a glorious chance to put the Hammers ahead when he nodded Mark Noble's corner wide when free in the box.
Noble then chipped over the wall to tee up Nolan, but his volley trickled inches wide.
That proved to be something of a wake-up call for Tottenham, who started the second half brightly.
Jermain Defoe, making his first league start of the year, finally managed to get in behind the Hammers defence, but Jaaskelainen came off his line to smother the striker's shot.
Spurs could still not turn possession into goals, though. Eriksen could not slip Defoe in again and at times the home side's passing was poor.
Vaz Te and Morrison shot wide as West Ham came into the game, and then the away side took the lead. Nolan unwittingly cleared Reid's goalbound header off the Spurs line, but the New Zealand defender swept home the rebound.
The Hammers fans were delighted and a blue flare was thrown onto the pitch from the away end.
Six minutes later, the away end was in uproar again as West Ham made it 2-0. Nolan carved open the Spurs defence with a beautiful pass to send Vaz Te through. His shot rebounded off Hugo Lloris' legs and he slid the ball home.
Villas-Boas threw on Roberto Soldado, but Spurs then amazingly slipped 3-0 behind after a fantastic solo goal from Morrison.
The former Manchester United man picked the ball up just inside his own half and drifted past Michael Dawson before lifting the ball over Lloris.
Tottenham fans started to leave in their droves, realising there was no way back.
The away fans, in contrast, sang "we want more" and Allardyce disappointingly asked the fourth official "is that all?" when he revealed there would be four minutes of added time.
The injured Carroll tweeted that he was "buzzing" about the result and that was certainly the feeling among the away fans at the final whistle as they reflected on a satisfying win.