Although uncredited Nicholas Courtney appears in the reprise from episode 2 making this the only story of the 1972 season in which he appears in every episode.
This episode takes place in England in the 22nd Century.
This episode was watched by 9.1 million viewers on its original transmission.
Although it is a production mistake Jon Pertwee credit being placed over the footage instead of the end credit sequence is the first time that this had happened since the 1960's and as of April 2018 this is the last time such a practice has happened.