Arsenal secured their biggest Premier League away win with a ruthless dismantling of West Ham to move back to within two points of leaders Liverpool.
Mikel Arteta's side stay third but are now behind second-placed Manchester City only on goals scored after wiping out a six-goal deficit on a stunning afternoon at the London Stadium.
It is West Ham's heaviest home Premier League defeat and joint-heaviest of all time, along with a 8-2 loss against Blackburn in 1963-64.
An extraordinary first half saw the Gunners race into a 4-0 lead, thanks to goals from William Saliba, Gabriel, Bukayo Saka and Leandro Trossard, leaving the home side stunned.