British Transport Police officers are appealing for information after a man unleashed a tirade of racist abuse towards fellow passengers on a train between Charing Cross and Waterloo East stations.
Officers are keen to speak to anyone with information about the incident, which took place at about 8pm on Thursday 21 November.
"One of the victims was approached by a man who launched a torrent of racist abuse towards him," said PC Jonathan Kenny.
"In a bid to get away, the victim changed carriages but the man followed him. He continued his abuse towards the victim and other people on the train whilst passengers urged the man to stop his vile language."
The incident was reported by another passenger and officers are keen to speak to the man who was followed through the train.
The suspect is described as thin and white, between 25 and 33-years-old, around 5'10, with short dark hair and a southern accent.
PC Kenny and his team are currently following a number of lines of inquiry, including looking at footage from CCTV cameras on board the train and at the station.
He continued: "This was a busy train and we know that there were people who stepped in, in a bid to stop this man. If you were on board the service at the time, we urge you to come forward as you may have information crucial to our investigation.
"We take all reports of racist behaviour very seriously, and will not tolerate it on the rail network."
Anyone with information is asked to contact British Transport Police on 0800 40 50 40 quoting background reference LSA/B15 of 3/12/2013. Information can also be passed to the independent charity Crimestoppers, anonymously, on 0800 555 111.