Dramatic footage which appears to show a policeman attacking a car after the driver refuses to get out will be investigated, Scotland Yard said.
The clip, shared on social media on Saturday and viewed thousands of times, shows what appears to be a police officer - filmed from the position of the driver - repeatedly telling him to "get out of the car", adding: "You're not allowed to drive it."
The officer then hits the driver's side window with what looks like a baton, before a voice can be heard saying: "I've got a licence. I've got a licence. I've got insurance. You're smashing this for no reason."
The policeman can be seen striking the windscreen, resulting in the glass shattering, and he then starts slicing around the damaged area with what appears to be a penknife.
When asked by the driver what the problem is, the officer tells him he is "not allowed to drive".
Leon Fontana, a 25-year-old mechanic, told the Press Association he was the driver and the person who filmed the footage.
He said the incident took place on Friday evening in the Gospel Oak area of north London when he had gone out on an errand for his mother.
He said it was a case of "mistaken identity", describing what happened as "a completely unlawful act".
Mr Fontana, who said he spent the evening in hospital due to getting glass in his eyes, said it was "complete madness" and that he is "still in shock".
He said: "Every time he smashed the glass, fragments of glass were just ricocheting in my face."
The Metropolitan Police said it is "aware of footage circulating on social media of an incident involving two uniformed officers in Camden", adding that the incident took place at Weedington Road, north-west London, at around 5pm on Friday.
In a statement, the Met said: "The footage will now be subject to an investigation by officers from the Directorate of Professional Standards (DPS)."
The police force said on Saturday evening: "As soon as the MPS was made aware of the footage, the DPS was contacted immediately. The individual who uploaded the footage has been contacted by DPS officers.
"As this matter is in its early stages, the officers have not been suspended or placed on restricted duties. No-one was arrested during the incident."
Mr Fontana said he is not sure when his car will be fixed and described the whole incident as "very stressful", adding: "I can't believe it to be honest. I can't believe it. I'm still in shock."
The video, which could not be independently verified, has been shared on Twitter and Instagram where the officer's actions have been described as "mindless vandalism and intimidation".