This episode rather cleverly subverts the idea of changing history. The Monk isn’t an outright villain. Like Barbara in The Aztecs, he wants to improve things, prevent wars, save thousands of lives and make things happen ahead of their time:

There wouldn’t be all those wars in Europe, those claims over France went on for years and years. With peace the people would be able to better themselves. With a few hints and tips from me they’d be able to have jet airliners by 1320. Shakespeare would be able to put Hamlet on television.

For any of the audience struggling to keep up, the Doctor spells out what’s happening: ‘So, you’re a time meddler’. And the Doctor plans to stop him – by ensuring that the English suffer their most infamous defeat. I really like that the Doctor is placed in the weird position of defending foreign invasion, war, and death on a vast scale just to protect the ‘golden rule’ never to interfere.

It’s unfortunate then that the negative implications of rewriting time aren’t as strongly articulated. Yes, war across Europe is awful – but if everything changes in 1066 Shakespeare wouldn’t have a history to write about. It would perhaps be more compelling for Vicki and Steven not only to realise that their memories would change – but that they themselves are likely never to exist at all. Trillions of future lives snuffed out on the Monk’s whim. As it is, they seem more concerned with the history books. Although I guess dwelling too much on this would distract from the humour of the conceit.

It’s also quite funny that the Doctor’s outrage at the Monk’s previous adventures – including inspiring Leonardo’s flying machine drawings – is exactly the kind of thing the fourth Doctor will proudly boast about in future.

The episode has some lovely comic bits – like the Anglo-Saxons chasing the Monk and his Viking friends in and out of the monastery, and the Doctor’s grumpiness about the Monk’s more advanced Mark Four time machine (it’s never called a TARDIS by him or the Monk). Even Sven and Ulf’s fate isn’t as grisly as originally intended thanks to a judicious cut that shows the Vikings getting their comeuppance without dwelling on the fatal aftermath.

Best of all is when Hartnell and O’Brien get to tell Steven, in unison, ‘History will be allowed to take its natural course’ just like Tom and Lis at the end of The Seeds of Doom. They really remind me of the Season 12 crew – a slightly incredulous new passenger watching two best friends having fun. I’m a bit devastated that this is pretty much the last I am going to see of this TARDIS team, because I suspect it could have been one of the best ever.

Next episode: Four Hundred Dawns