During the water-tank scene, the tank's glass cracked, sending broken glass and water across the studio towards the electrical equipment. By chance, Sylvester McCoy noticed in time to alert the crew. Sophie Aldred was pulled out in time and the studio was hurriedly evacuated. It is commonly believed by cast and crew that Aldred might have died if McCoy hadn't noticed in time; Gary Downie has said she was in no danger and it was only the floor crew at risk, although other cast/crew believed otherwise. Years later, McCoy would remember that day as the one time he himself was the hero instead of the Seventh Doctor.
This was the first UNIT (United Nations Intelligence Taskforce) story where the characters actually were many colors, genders, ethnicities, and decidedly "Not English".
This episode was watched by 3.9 million viewers on its original transmission.