Robert Pattinson's secret to onscreen chemistry apparently involves surprising your co-star in the nude.

The Twilight star - who has been catapulted onto the A-list by his blood-sucking role - jokes that in order to sizzle in front of the camera, he treated Kristen Stewart to an eyeful off set.

Robert tells Entertainmentwise, "I’d just walk into Kristin’s bedroom naked, just to shock her! (laughs) Not really. "

The actor also reveals that getting steamy vampire-style had its drawbacks.

He says, "It’s funny because we were both wearing contact lenses in the film.

"So much of those scenes relies on eye contact, and we had these ‘masks’ on our eyes so I was really worrying that there wouldn’t be anything there, so it’s very lucky that people thought there was."

Read the full interview

See a fully-clothed Rob at the London Twilight premiere below