‘Something’s coming, Bill. Something very big, and something possibly very, very bad.’ An episode that dwells on the death of Time Lords and the nature of reality. With plot points revolving around mass suicide, the Doctor hiding the truth from his companion, and powerful aliens creating a fake world as a test this could fit comfortably in Series Nine.

A lot of this darkness is offset a bit because Bill and Nardole bring an inherent sense of lightness and fun with them. Bill’s hapless lesbian date is interrupted by her foster mother, the TARDIS, and the Pope – her assertion that she and Penny have ‘nothing to feel guilty about’ looks a bit hopeless in that context. And Nardole – both in the flashback scenes where he acts as River Song’s messenger and the Doctor’s irritating Jiminy Cricket, and in the present when he’s forced to deliver humorously painful expository dialogue to the blinded Doctor – is brilliant. I love Matt Lucas’ channelling of Peter Davison, ‘must dash!’, while his reassuringly silly ‘I’m not real’ as he turns to pixels goes some way to making what’s quite a horrible scene less upsetting.

But this is still very grim stuff, even if it all turns out to be a simulation. In particular, the mass suicides, especially when Bill and Nardole get to CERN to find the scientists drunk and ready to blow themselves to bits. The mummified aliens look really creepy as they glide through the catacombs of the e-Vatican, like the desiccated corpses of the Capuchin Monks. The fact the episode looks spectacularly moody and sinister only adds to the tone of skin-crawling horror.

Then there’s Missy’s execution. The surprise reveal of who’s in the vault (or ‘quantum fold chamber’) isn’t exactly a shock, but as one of the highlights of this era it’s great to have Gomez back. There are emerging hints of a story arc for the remainder of the series as she promises ‘I’ll turn good’ in return for the Doctor sparing her life. I quite like the pay-off to this episode, but at the time I was concerned that, having done so much since Christmas 2015 to move the show on from introspective noodling, this threatens to plunge back into the excesses of the early 12^th Doctor.

Next Time: The Pyramid at the End of the World