Arsenal delivered an emphatic warning that they remain serious title contenders as they outclassed abysmal Chelsea at Emirates Stadium to return to the top of the Premier League.
The Gunners had gone four league games without a win and were heavily beaten last time out at reigning champions Manchester City, who replaced them at the summit with victory at Fulham on Sunday.
Arsenal responded by producing a magnificent first-half display, racing into a 3-0 lead inside 34 minutes courtesy of two crisp strikes by captain Martin Odegaard and a scrambled finish by Gabriel Jesus.
Chelsea, who fell to a sixth straight loss under interim manager Frank Lampard, were thankful to goalkeeper Kepa Arrizabalaga that the scoreline was not even more embarrassing and even pulled one back through Noni Madueke.