A have-a-go-hero has been shown on camera trying to stop an armed robber by leaping on his back and grabbing him by the neck in central London.

The member of the public ran towards the raider and briefly managed to stop him as he pulled out a machete.

The office worker then had to back off as the robber ran away.

The raider was in a gang of three wearing crash helmets who had robbed a jewellery store.

They had used a concrete block and sledgehammer to smash their way into the Liverpool Street shop and then tried to escape on two mopeds.

Two raiders managed to get on their bikes but when the third tried to get on the second moped, an unmarked police car attempted to block their escape.

It was at this point that the worker ran at one of the criminals, who had earlier been carrying a sledgehammer, and tried to bring him to the ground.

The plain clothes police officer, who had driven his car at the mopeds, also gave chase on foot briefly, before returning to his car.

Armed officers later caught the machete-wielding suspect in a nearby underground car park. The two other robbers are still at large, and police are warning they should not be approached.

But the actions of the passer-by are being praised, though police are advising others not to put themselves in danger.