Cole Palmer scored in the 10th and 11th minutes of stoppage time to secure an extraordinary comeback for Chelsea, sparking wild scenes at Stamford Bridge as manager Mauricio Pochettino led the celebrations at full-time.
Manchester United thought they had sealed their own turnaround after coming back from 2-0 down to lead 3-2, only for Palmer to strike twice against the team he supported in his youth to secure his hat-trick and the victory.
The fact that United were leading as the clock passed 99 minutes and 17 seconds meant this was the latest that a side has ever led in a Premier League match they have gone on to lose.