Doctor Who: 10 Best NuWho Villains That Only Appeared Once

8. Miss Hartigan

Episode: The Next Doctor

"In all these years not one of you has asked my first name," muses Miss Hartigan during the graveyard scene. "It's Mercy."

Human villains are few and far between on Doctor Who, or at least memorable ones are. But every once in a while we are treated to a human villain that blows all our expectations out of the water. Yet there wasn't much expectation for Mercy Hartigan leading into to the Christmas special of 2008. Nor did look good on paper, human ally of the Cybermen, been there, seen that. But what we saw in the finished product was a villain who outshone even the clunky steel bots.

While many Doctor Who baddies are notoriously OTT, the Daleks are about as subtle as a sledgehammer. Here we are given a lesson how a villain can be restrained, yet menacing. Dervla Kirwan turns in a fantastic performance, by convincing us that although she may not look it, Mercy Hartigan is as deadly and dangerous as the Cybermen.

Although it's never actually alluded too during the episode, the subtext hints at a terrible backstory including physical and sexual abuse. She thinks that allying herself with the Cybermen is a way for her to gain the power that she has been denied all her life. The real highlight of the episode, along with the interactions of the two Doctors, is the graveyard scene were she chastises the men, who are all gathered for a funeral, for never paying her a second thought.