Doctor Who star David Tennant has been banned from attending fan conventions by the BBC, because TV bosses fear the star may blurt out upcoming storylines to eager fans. The English actor is under contract to stay away from the sci-fi events, even though former Doctors Tom Baker and COLIN BAKER were allowed to meet their admirers in the past. He says, "It's just a precaution so that no storyline details are blurted out accidentally. "David's sorry for the show's followers but understands the reason."