ROBERT PATTINSON`s dirty secret has been exposed - he`s a smoker. And now he`s scared what his mum will say. The Twilight star has been enjoying sneaky fags on the London set of new movie Bel Ami. A source said: "Robert tried to make sure his security shielded him from lurking photographers. But a snap has appeared in America. "Robert`s since admitted he`s been scared about his mum finding out." I hope I`ve not smoked him out. Disgusting habit anyway.