A cyclist gave chase to three muggers who stole a man's bike, filming the group as they attempted to get away.
In the video posted on Youtube, you can see Alex Sweeting's brave attempts to pedal after the trio, who abandoned the stolen bicycle as he catches up with them.
Police are investigating the incident, in which a 53-year-old man was pushed off his bike and punched in the back of the head in Orient Way, Leyton, at 10pm on 17 March. The victim suffered bruising to his elbow and hip.
Anyone with information is asked to contact Waltham Forest police on 101 or Crimestoppers anonymously on 0800 555 111, quoting crime reference number 4905428/15.