British Transport Police officers are appealing for the victims or any witnesses following an altercation on board a London Overground train to contact them.
A video has circulated online showing two people in an altercation.
It is believed this has taken place on the London Overground line between Clapham Junction and Dalston Junction and was believed to be near Denmark Hill Station.
Anyone who has any information should contact British Transport Police by texting 61016 or by calling 0800 40 50 40, quoting reference 237 of 21 July.
Alternatively, you can contact Crimestoppers anonymously on 0800 555 111.
