It's a daily hazard for London pedestrians - impatient cyclists riding through zebra crossings.
But this man had clearly had enough - when a Lycra-clad commuter on a red bike tried to go through a crossing as people were walking over it, he confronted him.
The pedestrian had begun to cross just behind the biker, but rather than continuing across the road, he stopped and turned to physically confront him.
'Oi' he shouted. 'You have to stop, it's the law, it's the law'.
He then body-blocked the man on the bike from proceeding further up the road for several seconds, as other cyclists - who had halted at the crossing - looked on.
The yellow crossing lights were flashing as the incident happened on a road close to the Houses of Parliament in Westminster.
The video - apparently captured on the helmet camera of another cyclist - has been viewed nearly 28,000 times since it was posted online today.
According to the Highway Code, motorists and cylists must look out for pedestrians waiting to cross at zebra crossings and be ready to slow down or stop to let them cross.