Peter Capaldi’s final episode of Doctor Who this Christmas will feature Pearl Mackie as Bill Potts and be called Twice Upon A Time, it was announced this evening during a cast panel at San Diego Comic Con. Viewers will have to wait until Christmas to discover exactly how Bill, who will appear throughout the episode, makes her return.

It was also revealed that Mark Gatiss, who will co-star in the episode in a guest role, will play a World War One soldier - known so far only as ‘The Captain’.

As previously revealed in the closing moments of the 2017 series finale, the special will feature Peter Capaldi’s current Doctor team up with the First Doctor, played by David Bradley. 

Watch the teaser trailer in the player, below: