Mary Smith
From Tardis Wiki, the free Doctor Who reference
Mary Smith was an inhabitant of Ramón Salamander's underground community of scientists. In 2018, she didn't want Colin to go to the surface with Salamander. She later learned the truth about Salamander and was freed by Astrid Ferrier. (TV: The Enemy of the World)
Behind The Scenes
Her last name is only given in the novelisation.