West Brom destroyed Arsenal's chance to close the gap on Chelsea at the top of the Barclays Premier League with a thrilling 3-2 victory over the Gunners 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.
West Brom should have gone ahead in the 37th minute when Manuel Almunia brought down the speedy Odemwingie and referee Michael Oliver rightly awarded a penalty but Chris Brunt's poor left-footed effort was easily saved by Almunia, who dived to his right to keep it out.
West Brom took the lead in the 50th minute 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's double, the second coming in injury time, set up a frantic finish but it was not enough to prevent Arsenal slumping to their first home defeat since last January.