Story padding

Story padding was an integral part of the programme that the First Doctor featured in. He believed that the feature would remain the same for the "next twenty years".

In one million BC, whilst escaping from the Tribe of Gum, the Doctor explained to his companions that the story padding meant they would have to be recaptured and escape again five or six more times. (NOTVALID: An Unearthly Child: The Unscreened Edition)