Doctor Who finale leaked in US Saturday's episode, Nightmare in Silver was followed by a tantalising three-minute trailer for "The Name of The Doctor." It follows producer Steven Moffat's announcement that the finale instalment will "change the course of Who forever." News of the leak comes just as an eighth series of the show is confirmed by the BBC. It is expected that "The Name of the Doctor" will act as an unofficial prequel to the 50th anniversary episode, scheduled for November 23rd 2013. 'The Name of the Doctor' airs next Saturday (May 18) at 7pm on BBC One.