Chelsea had to settle for a point in a dramatic London derby at Stamford Bridge after losing a two-goal lead.
Cole Palmer’s penalty and Mykhailo Mudryk mis-hit cross left the Blues on course for a third consecutive Premier League win.
However, a mistake by keeper Robert Sanchez changed the course of the game, with Arsenal scoring twice in the space of eight minutes.
With Chelsea well on top, Sanchez’s appalling attempted clearance fell straight to Declan Rice, whose first-time strike pulled a goal back for the Gunners.
And Leandro Trossard equalised with a close-range finish at the far post from Bukayo Saka’s right-wing cross.
The turnaround came after Chelsea, much improved under boss Mauricio Pochettino, had been hugely impressive.
The excellent Palmer put them ahead from the spot after a VAR check led to William Saliba being penalised for a handball.
Three minutes into the second half, the lead was doubled when Mudryk appeared to be looking to cross for Raheem Sterling but embarrassed on-loan Brentford keeper David Raya, who was shaky throughout.
Chelsea: Sanchez, Gusto, Silva, Colwill, Cucurella, Caicedo, Gallagher, Fernandez, Palmer (James 84), Sterling (Madueke 84), Mudryk (Jackson 65).
Subs: Disasi, Badiashille, Ugochukwu, Petrovic, Maatsen, Washington.