‘I don’t just kill for money. It’s also something I enjoy.’ This is different: a historical set within living memory, practically within the show’s own lifespan. And not for the last time in the McCoy years. Again, this all unfolds with a pleasing sense of fun even when some of the subject matter is grim (the corpse strewn battlefield at the start includes a grisly moment when one of the bodies is blown up). The holiday camp setting isn’t unique (The Macra Terror and The Leisure Hive), but it’s a sensible choice – a microcosm of 1950s Britain. Alien tourists visiting Earth’s history for larks is such an obvious idea you wonder why Graham Williams didn’t get there first.

This is also a chance to bring the seventh Doctor down to Earth after his previous space adventures. If anything, he works even better in this context: McCoy brings a vulnerability that’s utterly charming, deciding to spend a night enjoying rock and roll rather than having to save the universe. McCoy is brilliant in the scene where the Doctor clocks Ray’s feelings for Billy and enthusiastically goes to the stage with her – only to realise Billy has eyes for someone else. The way he runs after Ray to awkwardly try to comfort her (even as he looks terrified of her emotions) is beautiful.

But this is all much less buttoned up than the show has traditionally been. The Doctor and Mel run through the Tollport holding hands; Delta might be a cold customer, but she thaws when faced with Mel’s relentless cheeriness. The Doctor and Mel, the Navarinos, even the Tollmaster (yay, Ken Dodd) just want to have a good time. It’s only horrid old Gavrok who’s spoiling everyone’s fun. The jokes are good (‘Wales, in England’), there are some nice touches like the chameleon arch that transforms a Navarino into a human (no pocket watches required), and the juxtaposition of green-skinned aliens warring on an (impressive-looking) azure-skied planet with 1950s holidaymakers dancing is the sort of story this series can do better than any other. There are stronger episodes of Doctor Who, but not many that make me happier.

Next episode: Delta and the Bannermen – Part Two