Believe it or not, "The Bells of Saint John" is the first official adventure Clara Oswald has with the Doctor. It might be her third appearance on-screen, but as far her influence over the Doctor's life and her travels in the TARDIS, this is where her story begins. And as befits a story that begins half-way through, there are threads dropped in this episode that remain un-picked for quite some time. How could she have lived three different lives? Who is the woman who gave her the TARDIS phone number? And did she REALLY think the internet was only available to one person a at time, on a first-come, first-served basis?

Here are a few things to keep an eye out for, the next time you watch:

(The episode is available on iTunes and Amazon.)

This is the second Doctor Who episode in a row (after "The Snowmen") to have been filmed with a specific prequel. In this case, it shows the Doctor in his trademark tweed jacket (for the last time), trying to figure out how best to find Clara Oswald:

https://www.youtube.com/watch?v=2IROtC6cAT4

In writing the script, Steven Moffat wanted to take the pace and tension of Daniel Craig's James Bond movies, or the Jason Bourne films, and use them to tell a very Doctor Who sort of story. He told Doctor Who Magazine he was interested in, "taking something omnipresent in your life and making it sinister, if something did get in the Wi-Fi, we'd be kind of screwed. Nobody had really done it before, so I thought, 'It's time to get kids frightened of Wi-Fi!"

The title of the story is taken in part from the nursery rhyme Oranges and Lemons ("say the bells of St. Clement's"), but with reference to the telephone in the door of the TARDIS, which also boasts the logo of St. John Ambulance. Due to a lack of international accord as to how best to abbreviate the word saint — British grammar omits the period, so "St John" rather than "St. John,;" U.S. grammar demands it — it was used in full.

Clara's leaf was originally intended to be a sheet of passport photos, suggesting that Clara had been halted in the action of applying for hers when Artie and Angie's mother died. This idea lingered right up until the finale was being written for The Rings of Akhaten, so that the leaf could represent Clara's entire life, not just her desire to travel.

When Mahler is checking the sighting of the TARDIS and says, "Are we sure this time? Earl's Court was an embarrassment," he's referring to the actual police box that resides next to the entrance to Earl's Court tube station.

[caption id="attachment_229292" align="aligncenter" width="460"] (Photo: BBC)[/caption]

To further add to Amy Pond's list of career achievements, Artie is seen reading the book Summer Falls, written by one Amelia Williams. The story was originally intended to be called One Deadly Summer. James Goss wrote a version of that story, and it was released as an ebook.

The very first scene filmed for this episode was never used. Nabile's video warning people of the dangers of wifi was originally shot at Roath Lock studios in Cardiff, with the actor Fady Elsayed playing the role. Due to Doctor Who achieving a more global profile, the clip was intercut with shots of Paris, London, San Francisco and Tokyo, which necessitated a reshoot at BBC Television Centre, this time with Manpreet Bachu as Nabile.

There was originally a scene in which the Doctor was called to the TARDIS phone a second time after Clara had been attacked by the Spoonhead, with a whispered female voice saying, "Run you clever boy. And save her." This was later changed to the voice saying he should trust Clara and take her with him, before being taken out entirely.

In mocking the Doctor's various invitations to join him in the TARDIS, Clara makes great use of the fine British slang term snog, meaning a kiss. She describes the TARDIS as a "snogging booth," referring to a carnival kiosk where kisses are (harmlessly) exchanged for money, and a "snog box," which isn't really a thing.

Having the Doctor ride his gravity bike up the Shard was a deliberate choice, to set the story in the immediate present. The skyscraper, situated near London Bridge, was quite a media talking point while Moffat was writing the script in 2012, and was opened to the public on February 1st, 2013, two months before this episode's transmission date.

https://www.youtube.com/watch?v=0OKvobPKN3Q

Incidentally, if you've a hankering to set up your own scary Wifi name, here's what you do:

http://doctorwho.tumblr.com/post/46758564991/howto-make-a-doctor-who-bells-of-st-john-style

NEXT: "The Rings of Akhaten"

Now go back and read the entire 10 Things You May Not Know About Doctor Who archive.