Inspirations: The Bells of Saint John

Three story arcs in play, two of which (spoilers) will merge at the end of this series. The third will take another year to materialise.

The first is Clara. We've seen Jenna Coleman, as she was then, twice so far - with similar names but in quite different time zones and on different planets. The last was a Victorian governess, who moonlighted as a barmaid (or a barmaid who moonlighted as a governess), and this new Clara is a childminder - so there might be a connection there. A barmaid could be said to work in Hospitality, and the first "Clara" we met was an entertainments officer on a spaceship, so Hospitality again.

The second arc is that of the Great Intelligence, last seen in a prequel to the Edward Travers arc of The Abominable Snowmen and The Web of Fear.

That third arc, which won't play out until Series 8, is the woman who gives Clara the phone number for the TARDIS (for the title of this episode refers to the ship's telephone, a Police Box also having a St John's Ambulance badge to indicate that it contains a first aid kit).

I'm sure a lot of people thought that this mysterious woman might be River Song, whilst every female villain is always going be the Rani. (It's been said that the villain of Series 15 is a woman, so might the Rani finally be coming back? A bit redundant after Missy, but you never know).

As with the Troughton stories and The Snowmen, the Intelligence makes use of something 'local' to act as its weapons - Yeti in Tibet and snowmen in a Victorian London winter.

In the first quarter of the 21st Century it's all about digital technology, and everyone is transferring from the old wired connections to Wi-Fi. The latest weapons are therefore mobile Wi-Fi hotspots - dubbed "Spoonheads" due to the concave shape of the back of the head.

Moffat stated that he deliberately wanted to use something everyone used in day to day life as a threat - something he's done often enough before and since.

Quite what the Intelligence wanted with the Earth we never knew. In its first outing it looked as though it was going to physically consume the planet, so perhaps feeding on natural energies of some kind.

It never looked as if it wanted human beings for any purpose, other than to have a single individual to act as its agent - Padmasambhava, Sgt. Arnold, Dr Simeon and now Miss Kizlet.

Here the Intelligence appears to be harvesting - what? Souls? Mental energy? Is it psychically eating people, or just enslaving them? It isn't entirely clear what its goal is.

London landmarks have played a part in Doctor Who's Earth invasions ever since Daleks were photographed on Westminster Bridge. After that we've had St Pauls (Cybermen), the Tower of London (UNIT), the London Eye (Nestenes), Big Ben (Slitheen), Gherkin (Sycorax), Thames Barrier (Racnoss), and Canary Wharf (Torchwood). 

Now the Shard is used.

This story is also the latest to feature a duplicate of the Doctor, companion or both - a feature of the series ever since the Daleks made an android Doctor in The Chase. It almost started even earlier, as the abandoned third story of Season One, "The Hidden Planet" by Malcolm Hulke, was to have featured a double of Barbara. Here, both the Doctor and Clara are copied by Spoonheads.

The story opens with the Doctor continuing his self-imposed exile, initiated by the loss of Amy and Rory. Hiding out in the same city and time zone as the Paternoster Gang probably wasn't a clever idea if you want to avoid adventurous entanglements, so the Doctor has relocated to a monastery in medieval Cumbria. No longer dwelling on the loss of Amy, he's now becoming obsessed with the Impossible Girl.

Once his interest is piqued and he returns to the fray, he abandons old habits (literally) and dons a new outfit. 

We see him admire a bow-tie in a box - one once worn by Patrick Troughton.

There's a topical reference to the London Riots of 2011, and mention of a mix-up at Earl's Court - a reference to the fact that there's a Police Box outside the Underground Station.

Next time: the Doctor faces the music, whilst Clara takes a leaf out of her mother's book...