A woman was reportedly throttled to the ground by a tour bus driver in central London following an argument over a mobile phone video.
The victim was a 27-year-old graduate at King's College London, the Evening Standard quoted eyewitnesses as saying.
She was attacked by the driver of a Golden Tours bus on South Bank on Tuesday after filming the vehicle allegedly jump a red light, the London newspaper reported.
Video footage of the incident, obtained by the Standard, shows the bus driver appearing to choke the woman, with bystanders attempting to separate the two women.
The woman is hearing shouting: "Let go of me; you have to let go of me," to which the driver replies: "You took my picture; delete my picture."
The graduate is then shown falling onto the pavement, appearing to lose consciousness momentarily.
The female driver, said to be in her thirties, turns on the crowd that has gathered before returning to her bus and driving off down Stamford Street – leaving the woman lying on the ground.
The Metropolitan Police confirmed it is investigating the incident.
"A 27-year-old woman reported to police that she had been assaulted by the driver of a tour bus," the force said in a statement on Friday. "No arrests were made and enquiries continue."
Andrew Basson, transport manager for Golden Tours, told The Guardian the driver had been supplied by an agency and her contract had now been terminated.
"We are absolutely distressed by this situation," he told the newspaper.
"This particular driver had been with us for three months and there were no problems so we're absolutely gobsmacked. Even more unusual is that is was a lady driver. All we can think is that it was a moment of madness."
Basson added CCTV footage from the bus had also been handed over to the police.