A video of a woman who appears to tell a passenger that his ancestors "used to be slaves" during an argument on the London Underground is being investigated by police.
The incident had erupted between the woman, who appears to be European, and the black man on the Jubilee line train between Stratford and West Ham.
The man can be heard shouting at the woman and he said she allegedly told him "don't touch me" after he accidentally bumped into her.
The woman can be heard to say: "You called me racist, I'm not racist. That is why people have a problem with you guys. I have black friends. I'm not racist."
"If you acted like a human being then I wouldn't have a problem with that. You have a problem because you guys used to be slaves," she added.
Other passengers joined in and shouted at her to "shut up" and "don't say that".
The man, dressed in a red blazer and black flat cap, tells her to use her "common sense" before shouting five times at her "you just called me a slave".
He walks away and the others continue to argue among themselves before he comes back and continues.
The woman then says: "You're a piece of s***. Honestly, I'm fed up with you guys" before she moves across the carriage and out of shot.
It is not known when the incident exactly took place but the video is being investigated, the British Transport police said.
A spokesman said: "Officers are currently analysing the video and are appealing for the person who recorded it to come forward."