Justin Bieber has taken London's nickname the Big Smoke literally - he was spotted in the U.K. capital wearing a bizarre gas mask on Monday (25Feb13).

The Baby hitmaker is in Britain for the U.K. leg of his world tour and he enjoyed a day out shopping in the city with his entourage.

But the singer baffled onlookers when he donned a creepy plastic and rubber gas mask, along with a leather suit and a baseball cap.

It's not the first time Bieber has been the man behind the mask - he donned a gold face covering last year (12), and tweeted fans to say, "i am the #masterofdisguise."