Speaking to the Telegraph, the bystander, who didn't want to be identified, said: "It was like watching a scene from a Guy Ritchie movie.

"These guys screamed up on the scooters and two of the pillion passengers jumped off and tried to smash their way into the displays with yellow axes. I think they grabbed a few watches.

"I waited for a second because I wasn't sure they had guns and when they tried to zoom off I grabbed one who was driving by the hoody.

He added: "Not putting his hoody up was a fatal mistake as it gave me something to get hold of.

"He swore at me and I managed to yank him off his machine. I thought 'this is my bloody city – why should thugs like this get away with it?'

"I hope the police manage to get the rest of them."