As the Twelfth Doctor nears regeneration, he stumbles on his first incarnation, also refusing to change. It takes a captain, a glass avatar and a familiar face to convince the Doctors the universe still needs them.

• BBC
• Peter Capaldi
• David Bradley
• Mark Gatiss
• Pearl Mackie
• Nikki Amuka-Bird
• Toby Whithouse
• Lily Travers
• Jared Garfield