Susan Jameson was originally cast as Morgan by Michael E. Briant. However, she was replaced by Tony Caunter when the BBC's Head of Drama Serials made an unusual intervention and decided the role was inappropriate for a woman to perform. Jameson was nevertheless paid in full.
This episode was watched by 8.5 million viewers on its original transmission.
This episode takes place on Uxarieus in March 2472.
The first episode since Jon Pertwee donned the titular role that doesn't feature Nicholas Courtney as the Brigadier.
The IMC robot was originally humanoid in design.