Snappers have exposed Robert Pattinson as a smoker.

And the 'Twilight' star is scared what his mum will say if she happens to find out about his vice.

The British heartthrob has been enjoying sneaky fags on the London set of new movie 'Bel Ami'.

"Robert tried to make sure his security shielded him from lurking photographers. But a snap has appeared in America," the Sun quoted a source as saying.

"Robert's since admitted he's been scared about his mum finding out," added the source. (ANI)