CCTV footage shows an 87-year-old woman being attacked and left with a black eye after a teenage girl punched her in the face.
The attack happened on the Route 166 bus in Croydon, South London. The girls were on board the bus without paying which started the argument.
They started arguing with the driver of the bus and the elderly woman, the Met Police said.
The victim can be seen standing near the pair before she was punched at around 3.20pm on Friday October 16.