An inspired West Brom battled to a thrilling 3-2 victory over Arsenal at the Emirates.
Three second-half goals from Peter Odemwingie, Gonzalo Jara and former Arsenal player Jerome Thomas put Albion in front before Samir Nasri scored two late goals for Arsene Wenger's side.
It was Arsenal first home defeat since they lost to Manchester United last January and kept them four points adrift of leaders Chelsea while Albion moved up into fifth place.
The writing was on the wall for Arsenal in the opening half despite dominating the early exchanges. Andrey Arshavin should have put the home side in front but he managed to hit the post twice when he got on the end of a cross from Emmanuel Eboue.
West Brom grew in confidence and Odemwingie saw Manuel Almunia push his angled drive onto the post. But in the 37th minute the keeper brought him down and referee Michael Oliver awarded a penalty - only for Chris Brunt to send in a poor effort that was easily saved to Almunia`s right.
They visitors took the lead after 50 minutes when Thomas wriggled free on the left flank and crossed into the six-yard box for the unmarked Odemwingie.
It got worse for the home side two minutes later when Almunia blundered to allow Albion to make it 2-0.
Brunt set Gonzalo Jara free on the right and his low angled drive from the right edge of the penalty area went through Almunia's hands and into the net.
West Brom sensationally made it 3-0 when Brunt crossed for the livewire Thomas to fire into the net in the 73rd minute.
Nasri danced through to reduce the deficit and added his second in injury time but it was the visitors` day.