At the beginning of The Powerful Enemy, the story started with Vicki awaiting rescue – and then followed what happened when the TARDIS crashed into her world. The Watcher takes the opposite approach, starting with the Doctor and Vicki discussing Ian and Barbara’s departure, and a touching moment when the Doctor asks Vicki if she wants to go home and she laughs off the idea: ‘I made my decision.’ And then, into their world crashes Steven, initially revealed as a shuffling, ragged creature before the camera pans up.

This sets the scene for an episode that expertly balances comedy and suspense. Vicki and the Doctor team up to take the mickey out of the new boy, although he probably deserves it for his arrogant dismissal of the idea of the TARDIS. It’s all a lot more good natured than the similar sequence in An Unearthly Child (Susan gets to explain the initials TARDIS just as Susan did – although Vicki claims the D stands for Dimensions plural). Hartnell gets the most brilliantly catty lines – ‘sheer poetry in motion’ and ‘a space helmet for a cow’ in particular – in a brilliant, smart script.

There’s a very funny moment after the TARDIS lands on a beach where, having boasted about it, the Doctor and Vicki have to grumpily wave away the TARDIS’ broken camouflage unit and directional controls as a ‘slight technical hitch’, much to Steven’s evident amusement . But this also acts as a clever restatement of the TARDIS’ abilities which are going to become important in later episodes.

This episode is functioning on a lot of levels, It introduces Steven as a sceptical, hot-headed upstart unlike the rather more respectful and cautious Ian. Once the Doctor heads off to explore, Steven immediately ignores his orders and decides to climb to the top of the cliffs, and then later he ignores Vicki’s sensible suggestion to lie low until they’ve worked out where they are and instead gets into a scrap with an Anglo-Saxon.

It also introduces the theme of anachronisms – the TARDIS itself, clearly, but also the mysterious Monk who’s evidently lost a wrist watch, and whose monastery has a switch-on electric light and a gramophone. The last two are witty ideas that a smart audience might initially think are hallmarks of a shoddy production – the cliché of a candle suddenly switching on to illuminate a room, and a dodgy record to represent the monks’ chanting are finally revealed to be exactly that, and Douglas Camfield or Dennis Spooner to have outfoxed the critical viewer.

Hartnell is slightly more fluffy – in every sense – than normal, but is also thoroughly charming as he trounces Steven, woos an Anglo-Saxon housewife, and finally decides there’s something fishy going on at the monastery. He does talk to himself a lot more than usual – but possibly that’s just because he’s had a bit too much mead.

Meanwhile, despite having only five words in the whole episode, Peter Butterworth makes the Monk both mysterious, silly (his evident fluster when he goes to check his watch and realises it’s gone), and even dangerous – setting a perfect trap for the inquisitive Doctor. The cliffhanger, which subverts all the expectations of the historical stories to date, and puts the Doctor face to face with a new type of villain, is one of the best yet – it must have got people wondering what was going to happen next.

Next episode: The Meddling Monk