Detectives investigating an assault on board a London Overground train are looking to identify him in connection.
The assault happened at around 8.34pm on 19 August, on board a Homerton to Stratford service.
During the journey, the victim and another man had a argument. The exchange of words became aggressive, with the victim being punched a number of times to the head and body.
The victim suffered a number of cuts and bruises to their face, as well as a fractured cheek.
Officers believe the man shown in this CCTV image may have information which could help them investigate. If you know who he is, contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 625 of 19/08/2019.
Or you can call Crimestoppers anonymously on 0800 555 111.