Doctor Who: 10 Defining Moments Of The Ninth Doctor

6. In The Name Of The Father

The Doctor knows which events can be changed and which ones can't (although this isn't always set in stone as viewers would later discover in the Tenth Doctor episode The Waters of Mars) and in Father's Day his morals were tested when he took Rose back in time to witness the death of her father. It sounds cruel when you put it like that, but his intentions were good. Unable to resist temptation, though, Rose intervened with her father's death which resulted in the deadly Reapers being unleashed on Earth to sterilise the wound in time. In his coveted position as the last of the Time Lords, though, the Doctor attempted to settle things but not before partaking in a gritty argument with Rose in which he outlined the consequences of interfering with time. Towards the end of the episode, the Doctor came to realise that it's something that his companion needed, not wanted - she needed to see her father, for reassurance and closure, and the Doctor stepped back as Pete sacrificed himself to save time and Rose was there to hold his hand in his final moments.