Arsenal's recent run of good form came to an abrupt end as Queens Park Rangers picked up a vital win at Loftus Road.
Adel Taarabt and Samba Diakite scored either side of Theo Walcott's leveller to end the Gunners run of seven straight league wins.
The visitors had the game's first real chance when Robin Van Persie's clever free kick almost caught Paddy Kenny out at his near post on eight minutes.
Challengers were fiery as the London derby heated up and Mikel Arteta was lucky to escape without a card when he caught Joey Barton in the face with a boot.
From the resulting free kick the ineffective Bobby Zamora missed a glorious chance to head the R's ahead, when he was found unmarked from six yards.
Midway through the first half Rangers took a deserved lead when Taarabt smartly turned Thomas Vermaelen and curled past Wojciech Szczesny to send the Loftus Road faithful into raptures.
Their lead only lasted 15 minutes however, Walcott hit the post from the edge of the box but fortunately for the winger it came straight back to him and he notched home his 10th goal of the season.
Aaron Ramsey almost instantly put Arsene Wenger's side ahead, the Welshman's strike clipping the past on its way wide.
Van Persie had a glorious chance to make it 2-1 Arsenal when he found himself one-on-one with Kenny but the Ducthman couldn't generate enough power to worry Kenny.
As Arsenal were building some serious pressure and taking the game to the hosts the inevitable happened, Jamie Mackie found himself free on the edge of the box and he sqaured for Diakite who cooley slotted home his first QPR goal.
Barton almost made it 3-1 late on but Szczesny did well to tip the ball over the bar.