The black-and-white images shows Mr Tam being approached by a male assailant and then walking onto the road in an attempt to get away. The hooded attacker then chases Mr Tam across the street - running in front of an oncoming car, which is forced to stop - before catching him and forcing him to the ground.

He then appears to strike Mr Tam on the head at least twice with an object before grabbing his bag and running away.

Mr Tam lies prone in the middle of the street for several seconds before trying to get up. In the immediate aftermath of the assault, police called his injuries “severe” and “life threatening” .

The incident - which lasted for less than 20 seconds according to the video footage - appeared to be witnessed by at least two motorists, including the driver of the car which stopped after Mr Tam and his assailant ran in front of it.