Doctor Who: 10 Best NuWho Guest Stars Ever

Villains can make for just as compelling performances as heroes - if not more so - and Harry Lloyd's appearance in the Series 3 two-parter Human Nature/The Family of Blood is one of the best that NuWho has to offer. Playing the apparent ringleader of the titular family, he is creepy in a way that will haunt nightmares for a good long while.

Lloyd starts off as Baines, one of the posh pupils at the school where the Tenth Doctor (in human form) has become a ringleader. He is taken captive by the Family of Blood and possessed by one of them, mostly referred to as Son of Mine. Lloyd plays the character's ruthlessness, disregard for life and lust for immortality brilliantly, leaving viewers in no doubt that the Doctor and Martha were dealing with a particularly intimidating and sadistic villain.

However, the real brilliance of Harry Lloyd's performance comes in what he does to seem alien. His movements and actions don't quite come across as human and he creates little tics, such as the way the character sniffs and the fact he rarely blinks, that create an impression of an alien possessing a body that is not entirely familiar to it. As a result, he manages one of the most effective alien performances to date.