West Ham United shattered Arsenal's unbeaten record at Emirates Stadium thanks to Bobby Zamora's goal, but Robert Green was in inspired form for the Premiership strugglers.
Zamora's cool finish in first-half injury-time earned The Hammers a third consecutive win in a game which seemed to encapsulate Arsenal's season.
Green produced a series of stunning saves to thwart The Gunners, who also hit the woodwork twice as Arsene Wenger's side slipped to a first defeat at the Emirates.
Coincidentally, West Ham were also the last team to beat Arsenal at Highbury and the three points will heighten hopes Alan Curbishley can lift the club out of the relegation zone.
West Ham spent much of the opening 20 minutes chasing shadows as Arsenal's clever movement and incisive passing pulled the visitors this way and that.
The Gunners could have been in front inside two minutes as Freddie Ljungberg and Tomas Rosicky combined to release Cesc Fabregas, but the young Spaniard's shot was smothered by Green.
The Hammers keeper was overworked in the early stages as he held Emmanuel Adebayor's curling effort after the striker had made a mug of James Collins.
Opportunities continued to come Arsenal's way as Adebayor lifted his shot over the bar from a Ljungberg pull-back before Green proved his worth again.
Rosicky's precision pass sent Ljungberg between the two centre-halves, but Green was out quickly to block the Swede's attempt.
Emmanuel Eboue and Alexander Hleb were then involved in a clever move to set up Rosicky, but he sliced his left-footed shot wide in front of goal.
West Ham were limited to rare counter-attacks, but were unable to test Jens Lehmann as Rosicky arced another shot wide at the opposite end.
Green then produced a sprawling save from Rosicky's thumping drive before Nigel Reo-Coker's poor pass denied Carlos Tevez a run on Lehmann's goal.
Fabregas' impudent chip failed to catch out Green before The Hammers took the lead in injury-time at the end of the first half.
Lucas Neill's long pass sent Zamora - possibly from an offside position - clear and the striker lifted a superb lob over the exposed Lehmann.
The second half followed a similar pattern to the first, but not before Zamora's knock-down saw Lee Bowyer drill a first-time shot into the arms of Lehmann.
From there, Green waged a one-man battle to keep Arsenal at bay - and West Ham in the Premiership - as he produced several important saves.
After the ball fell kindly for Gilberto Silva, the Brazilian's low shot from the edge of the area was brilliantly turned round the post by Green.
And the Hammers keeper then conjured up an even better save as Adebayor was allowed to steal in unmarked to meet Fabregas' free-kick, but his header was magnificently kept out by a one-handed reflex stop from Green.
Arsenal finally found a way past Green on the hour mark, but Fabregas' turn and shot from the edge of the area crashed back off the crossbar.
Gilberto then headed a golden chance wide from close range after Eboue's cross had been diverted onwards by Anton Ferdinand.
Jeremie Aliadiere was introduced for Hleb and the substitute had an immediate chance to equalise, but shot into the side-netting after the ball rolled invitingly into his path.
Green produced a flying save to catch Fabregas' header and then had the post come to his rescue as Gilberto's prod, after Julio Baptista had flicked on Rosicky's cross, clipped the upright.
West Ham, for all they were hanging on, could have stolen a second goal late on as Mark Noble's pass played in Luis Boa Morte, but the substitute's dink was over Lehmann and wide of the target.