While filming a scene in which their characters get into a physical confrontation, Brian Blessed actually punched Peter Capaldi in the face so hard he knocked him unconscious.
Features 17 Doctor Who actors, including two Doctors - Peter Capaldi and Sylvester McCoy; also Camille Coduri, Lindsay Duncan, Brian Blessed, John Sessions, Ron Cook, Celia Imrie, Matt Bardock, Tessa Peake-Jones, Roger Lloyd Pack, Brian Hibbard, Soo Drouet, Tim Barlow, June Whitfield, Rupert Holliday-Evans and Alexei Sayle.