In Terry Nation's original ending, the Daleks and the Thals were both confronted by a race of beings from another planet, who revealed that it was their ancestors who had actually fired the neutron missile which had devastated Skaro centuries earlier. Their people had since realised the error of their ways and sought to help both the Daleks and the Thals rebuild their shattered civilisation.
In the original script, the Doctor and Susan were sentenced to be executed in a "Sonic chamber".
In the original script, much was made of a forthcoming "great rain" - a periodic meteorological event on Skaro - which would reduce the radiation levels enough to permit the Daleks to emerge from their city and confront the Thals.
The negative is a dub from the positive print.
This episode was watched by 10.4 million viewers on its original transmission.