Michael Craze found working in fake snow difficult, he had just undergone surgery to remove a bone chip from his nose during which he suffered a burst blood vessel which nearly cost him his life) and the jabolite "snow" blown around the film stage irritated his nose badly.
Michael Craze met his future wife, production assistant Edwina Verner, on this story. She threw some of the polystyrene 'snow' into his face as a practical joke, inadvertently aggravating an injury he had recently sustained to his nose.
The first ever appearance of The Cybermen.
This episode takes place in Antarctica in December 1986.
The fourth episode is missing from the BBC archives and is listed as one of the top ten missing British television programmes, alongside the BBC news studio commentary from the Apollo 11 mission.