This is the shocking moment a furious mixed-race teenager tried to hit a woman on the Tube after she made a racist remark.
The mobile phone footage posted on YouTube yesterday is entitled 'Racist Woman On London Train Gets What She Deserves!'
It begins a short way into their argument - after the 19-year-old aspiring recording artist had apparently stepped on the woman's shoe.
The pair trade insults, with the boy shouting that the woman has been racist, and her then calling him a 'smelly Nigerian', before he compares her to an 'escort'.
Their expletive-littered argument then descends into violence, with the teenager lunging at the woman after accusing her of having hit him with a bottle.
Eventually, the Tube driver asks what is happening over the intercom, and the three-minute video comes to an end as the fight is broken up.
A Twitter user known as Cidz Carnage or @carnageofficial, thought to be the youth involved, tweeted on Tuesday: 'Oi some racist women was giving it to me today, then she hit me with a bottle then i f***ed her over dumb b****.'
He later added: 'Calling me a smelly african... Then having the audacity is hit me with a bottle.'
And yesterday he posted: 'Remember Racism is Disgusting and Totally Unacceptable'.
He later deleted the tweets.
British Transport Police believe the video was filmed on Tuesday and posted online the next day.
A BTP spokesman said: 'There is an allegation of abusive behaviour by the woman towards the man, but that doesn't justify a violent response.
'The man and woman pictured in the images are seen arguing with each other on the video and we're keen to speak to both of them to get their version of events.
'We urge them or anyone who knows them, as well as passengers who were on the train at the time, to come forward so we can begin to build a full picture of what exactly took place.'
They are appealing for information about the incident, believed to have taken place on a southbound Northern line service between Old Street and Moorgate.
The footage begins with the woman, who appears to be in her 20s, saying: 'I wouldn't f***ing touch you. You are f***ing s*** on my shoe' and adding that her boyfriend is black, suggesting that this shows she was not being racist.
'He respects me,' she continues, after the boy had apparently insulted her appearance.
The teenager replies: 'OK white princess, queen, Kate Middleton!
He criticises her 'lunatic antics' and calls her a 'smelly p**** b****', adding: 'How old are you, 28? I'm only 19.'
She expresses concern that 'b******s like you will steal from me' and calls him a 'smelly f***ing Nigerian.'
He becomes increasingly angry at her lack of remorse, asking: 'So first I pushed you, now I've tried to rob from you?' He compares her behaviour to something that would happen in America.
A moment later, she says: 'I don't care what I look like', apparently in response to another insult.
As the train pulls in to Moorgate, a fight breaks out, with the boy seen lunging at the woman, shouting, 'You hit me on the head with a bottle... you racist b****... looking at you, you f***ing escort. There are witnesses. Everyone seen, everyone heard!'
He is pulled away from her as voices are heard saying 'relax' and 'let her go'.
He appears to leave, adding: 'don't you ever touch me, don't you dare touch me.'
The incident follows a recent spate of passengers filming racist rants on public transport.
See the video footage below: