Actor Daniel Radcliffe has found a new way to greet his fans - sneaking up on them while they're in the middle of being interviewed about his latest film, What If. 

Radcliffe stars as Wallace in this When Harry Met Sally-style film that sees him meet the girl of his dreams, only to learn she already has a boyfriend. 

After fans were treated to a screening of the film, they were asked to share their thoughts on it to camera. But then, along comes Mr Radcliffe himself. 

Their reactions? Well, there's a whole lot of swearing. Radcliffe certainly needn't worry about his popularity. 

Check it out here: