CCTV footage shows the moment a woman tried to stab a 15-year-old boy with a huge kitchen knife as he boarded a bus with his grandmother.
The incident happened on Boxing Day at around 12.30 pm on the Route 133 bus on Brixton Road in Lambeth.
The attacker, who was already on the bus, came up to the teenager and attacked him with a large kitchen knife.
The victim's 51-year-old grandmother managed to wrestle the weapon off the attacker, who then fled towards Oval.
The victim suffered a minor cut to his stomach. The suspect is described as:
an Asian woman
aged about 20 to 30 years
wearing a distinctive headscarf with a kangaroo print
Anyone who was on the bus at the time of the incident or has any information, has been urged to call police via 101 or Crimestoppers anonymously on 0800 555 111 quoting reference 199092.