Besides the two-part finale (which is Doctor Who’s version of Avengers: Endgame ten years earlier) “The Fires of Pompeii” is probably my favourite episode in series four. Well, there’s also “Midnight” which is pretty fantastic but “The Fires of Pompeii” pips it to the post because of how it really sets up the Doctor’s and Donna’s relationship and there’s the inevitability of a major historic event poised to happen at any moment.

The historical episodes really worked for me and having the ticking time bomb of Mount Vesuvius set to explode at any moment in “The Fires of Pompeii” added some great tension but also emotion to the story. You spend some time with the people of Pompeii, and one family in particular, putting faces to this tragedy caused by nature. I learnt about Mount Vesuvius at school so this episode put into focus some of the facts and figures and stuff I only knew about in the abstract before.

Part of the point of companions is to challenge the Doctor but Donna did it in a way unlike we’d really seen before. She’s not afraid to shout at him in the street and him being an almighty Time Lord means nothing when there’s lives on the line. Plus, there’s the moment where he has to make the impossible decision – push the button to set off Mount Vesuvius and save the world, but in the process cause the destruction of Pompeii and kill everyone who lives there – and Donna is right by his side, sharing the responsibility and guilt of that decision.

Fixed points in time are something that’s mentioned a lot in Doctor Who. They’re moments in history that can’t be changed because if they are, there will be terrible consequences. In “The Fires of Pompeii” this means that a city and its people have to be destroyed to preserve the timeline. I love how Donna begs the Doctor to just save one person, just one person out of thousands can’t destroy a fixed point in time, and he does. And though there’s no way the writers would’ve planned for it at the time, that decision had consequences for the Twelfth Doctor and his story arc which was pretty cool way to explain how an actor has appeared in the show more than once.