Doctor Who: Every Tenth Doctor Episode Ranked From Worst To Best

The idea of a world without the Doctor to protect it - pitched as a Sliding Doors moment where Donna was unable to save him - had the potential to be one of the most darkly fascinating Doctor Who stories ever.

And you know what, it was.

Watching the alien invasions of previous stories as the Doctor is unable to stop them, from the helpless point of view of Donna, is horrifying and intriguing in equal measure. It's always risky when the Doctor isn't in your Doctor Who episode, but audiences were already deeply invested in Donna by this point, so Turn Left worked a treat.

Not to mention the reappearance of Rose as Donna's 'guardian angel' so to speak, which further ensures that the Doctor's absence isn't to the episode's detriment. Also terrific is Bernard Cribbins (surprise surprise), who was starting to cement his position as the MVP of Tennant's final year. His tearful goodbye to the Colasanto family is a Doctor Who moment that's difficult to forget.

Although not strictly a three-parter, Turn Left does also cleverly lead directly into The Stolen Earth, and sets up the stakes well for the epic Series 4 finale.