Part of what has made Doctor Who such an accessible and beloved show with the kind of longevity other television can only dream of is the concept of regeneration – it’s much easier to endlessly reinvent yourself and pick up new fans if your lead character can become anyone every few years. There’s a pantheon of prestige actors who have embodied the role as well, especially post-revival: Christopher Eccleston, Matt Smith, Jodie Whittaker, all maj…