All four parts of this story were found in 1993 after being considered destroyed for 23 years.
This is the earliest Second Doctor serial which still exists in its entirety.
Cybermen created by Gerry Davis and Kit Pedler.
This is the only original complete serial to feature Victoria Waterfield (Deborah Watling).
This episode attracted 6 million viewers on initial broadcast.
The Doctor: Well now I know you're mad, I just wanted to make certain!
The Doctor: (after disabling the Cybermats) The power cable generated an electrical field and confused their tiny metal minds. You might almost say they've had a complete metal breakdown.
The Cyber Controller: We will survive.
The Cyber Controller: You belong to us. You shall be like us.