The latest Doctor Who Christmas special had a lot going for it. It was Peter Capaldi's final hour, it saw him team up with David Bradley's First Doctor, Pearl Mackie's Bill returned and there was even a guest role for Mark Gatiss. Despite all that, however, the biggest talking points were that one, we finally saw Jodie Whittaker's debut as the Thirteenth Doctor in the episode's last few moments, and two, a very special individual returned to see Number 12 off.