Four officers were injured after coming under attack by a gang of about 100 youths.
Bottles and missiles were thrown at police by a 'hostile' crowd outside the Pret a Manger cafe near Stratford Station on Saturday at 7.50pm.
Video footage shared on social media shows officers running towards a group of youngsters gathered on the station forecourt with one man carried off by police before a projectile is chucked at them.
A Met spokesman said: "Four officers were injured after police responding to reports of a robbery were met with hostility by a large crowd."
A woman was injured when she fell down the stairs at the entrance to the underground. Police described her injuries as not life threatening.
Three people were arrested, two on suspicion of being in possession of an offensive weapon and one on suspicion of robbery.
The three remain in custody at an east London police station.
One boy was found with a hunting knife after being stopped by police when he tried a flee the scene.
A Section 60 order, giving police powers to stop and search, was in force in Stratford until 3am on Sunday.
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