Julian Bleach as Davros in The Magician’s Apprentice/ The Witch’s Familiar (2015).
Once upon a long ago, according to Ghost Light (1989), an elemental being called Light took it upon himself to catalogue every life form in the universe. But there was a problem. “Everything is changing,” grumbled the luminous one. “All in flux. Nothing remains the same.” (For someone who travelled at the speed of thought, Light was curiously slow to catch on.)
“That’s life,” shrugged the Seventh Doctor. And he should know – because, in the universe of Doctor Who, it’s fair to say that change is the only constant.