Cristiano Ronaldo scored his 800th career goal before driving home a penalty winner as Manchester United came from behind to beat Arsenal in a memorable contest featuring two crucial VAR decisions.
As new United interim boss Ralf Rangnick watched from the directors' box, where former England captain David Beckham also enjoyed a thrilling encounter, Arsenal scored first in controversial circumstances.
Emile Smith Rowe drove home from the edge of the area, while United keeper David de Gea was lying on the ground, seemingly injured, with his back to play.
The inevitable VAR check concluded De Gea had fallen after bumping into and being trodden on by his own team-mate Fred, and referee Martin Atkinson gave the goal.