‘If you don’t like it then bog off.’ Light is defeated in the same way as Dr Johnson in Blackadder the Third, by the hero pointing out gaps in his catalogue. This is more straightforward than the first two episodes, offering some necessary clarifications around Smith and Light’s separate plans (although how Smith thinks assassinating Queen Victoria will allow him to ascend the throne still less overturn Parliament is anyone’s guess).

This isn’t the only thing that makes almost no sense if you stop to think about it. Light knew about evolution before he’s discovered everything has changed since he finished his catalogue (‘I once spent centuries faithfully cataloguing all the species there, every organism from the smallest bacteria to the largest ichthyosaur. But no sooner had I finished than it all started changing’) so why is the fact of it now enough to drive him insane? I guess because it’s changed so much he’ll have to start again? Is evolution unique to Earth though? It’s a good job Light never visited Alzarius or Skaro.

More troublingly: why did the Doctor think releasing an insane angel was the best way to stop Smith? As a result of his interference, two maids, a Scotland Yard inspector, Mrs Pritchard and Gwendoline all die and the Earth nearly gets nuked. How did the Doctor realise Light is going to destroy Earth before Light announces it? Why does he suddenly gurn and clench his fist like he’s having stroke when chatting with Light?

To be fair, you can nitpick nearly any Doctor Who story to bits, and, like Time and the Rani, if you overlook the scrappy plotting and don’t ask too many questions it all looks great. It has some vivid, brilliant images (Light holding a maid’s arm and announcing, ‘I wanted to see how it works so I dismantled it’), very funny jokes (‘the cream of Scotland Yard’) and excellent performances and design (Light looks like it’s walked out of a William Blake illustration). It also has Ace breaking down and confessing she burned down Gabriel Chase a few minutes after a brilliantly disconcerting flashback to that night (firelight and police sirens), even if Sophie Aldred has to deliver ‘You’re not my probation officer’ with a straight face. The final exchange (‘I wish I’d blown it up instead’; ‘Wicked!’) is superb.

Next episode: The Curse of Fenric