‘But they were French. It’s not my fault if “Danger Explosives” was only written in Welsh.’ My favourite RTD episodes are the ones that don’t have to “do” something – open or close a series; celebrate an event; change the regular cast. Boom Town is the first of a select group that also includes Love & Monsters, Gridlock and Midnight. Conceived to be budget-conscious ahead of the finale, necessitating more dialogue, less action, RTD picks up the gauntlet thrown down by Moffat and writes the funniest episode of the series.

From the off, it’s set up as an Aliens of London sequel. There’s no secret that Margaret Blaine is actually Blon Slitheen, and her wicked sense of humour remains undimmed. RTD gets the fart jokes and Slitheen unmasking out of the way early so that he can get on with the real story he wants to tell: a light morality play riffing on ideas of nature versus nurture, redemption versus retribution and what the Doctor has in common with the monsters.

A lot of the themes that come more sharply into focus across the next three series crop up here, particularly the consequences of the Doctor’s lifestyle. Margaret accuses the Doctor of, ‘Always moving on because you dare not look back’ just as Davros will in Journey’s End. She also suggests his whims decide who lives and dies, prefiguring Joan Redfern and Mr Copper. She even has a Professor Yana, ‘Does it matter?’ when the Doctor quizzes her on how she came up with ‘Blaidd Drwg’. Oh, and Mickey says, ‘‘I knew we should have turned left.’ So many little hints of things to come.

I like the human scale of this. Margaret’s execution might be deserved, but none of the companions can look her in the eye and end her life. Mickey’s own life is a mess because Rose swans in and out of it on a whim. For the first time, Noel Clarke gets to play Mickey with real anger and hurt, while also making him a clumsy oaf. I particularly like that Rose seems to have gone to some effort to dress up for him, with her hair in unutterably cute plaits. There’s a current of her keeping him keen while treating him mean, but the way she runs off to look for him at the end, and recognises he deserves better saves her from looking like a self-absorbed madam.

This is much better than it needed to be for the cheapie episode. Joe Ahearne makes the Slitheen look more impressive than in Aliens of London (even though there’s no-one around to see it), and the costume seems to have been slightly augmented, able to convey sadness with some (presumably GCI) blinking. The ‘dinner in bondage’ scenes in the restaurant are my favourite ninth Doctor moments, as Eccleston and Badland play it with faux politeness and charm. The galactic surf board, last-minute end of the world twist and (literal) deus ex machina ending are cursory, but because they aren’t the focus of the episode I think RTD gets away with it.

Instead, we get our one real sense of how the Doctor, Rose and Jack might work as a team (in a sort-of Torchwood pilot); Eccleston, Piper and Clarke get some of their best character material; Badland’s brilliant villain gets an encore, and the ‘Bad Wolf’ and heart of TARDIS moments set up the final two-parter. It might be my favourite ninth Doctor episode.

Next Time: Bad Wolf