10 Saddest Doctor Who Companion Departures

Susan's departure isn't too sad. She leaves of her own choice after falling in love but it's the Doctor's goodbye monologue to her that is most poignant. Everyone knows the "One day I shall come back," line but what makes it even more sad is that if we just count the main show as the official canon, he never did.

William Hartnell often struggled on set but he and Carole Anne Ford, who played Susan, were very close. They even remained close friends after she left the show, so he was obviously sad when she left and that can be felt in his goodbye speech.

Even more sad, is that it shouldn't have come down to this but Carole Anne Ford explained she had been promised a cool character with telepathic powers and she was meant to be like an Avengers girl and have a great wardrobe. When none of that came to fruition, Ford felt cheated and decide to leave. Who can blame her?

Still, we'd have loved to have seen more of Susan and the fact that the Doctor just abandons her to a normal life is very tragic.