The second half of Season One's first two-part adventure sees the Doctor make a hero out of Mickey, a Prime Minister out of Harriet Jones and turn down the offer of shepherd's pie from Rose's mum Jackie. All in a day's work for a meddling Time Lord.

Here are a few things that you should keep an eye out for, the next time you watch. (The episode is available on iTunes and Amazon.)

One of the reasons Russell T Davies set this particular tale in 10 Downing Street (the official residence of the British Prime Minister) was the video for the Girls Aloud single "Jump," which contains footage of Hugh Grant dancing through the building, taken from the movie Love Actually. Of course, in Doctor Who there is less dancing and more running.

https://www.youtube.com/watch?v=rk7zhB_m4gc

The Doctor gives a little history lesson about Number 10 and Downing Street (including the reference to previous owner, the enigmatic Mr. Chicken), but leaves out a few fascinating facts. The street was named after Sir George Downing, Anglo-Irish statesman who was educated in New England and one of the nine first graduates of Harvard University in 1642. During the English Civil War he worked for Oliver Cromwell in intelligence and had the wonderful title of Scoutmaster General. When Cromwell died and governance was restored to the royalty, he swore loyalty to Charles II, like any good diplomat would.

Also, if it seems abnormally big for a terraced house, 10 Downing Street is actually two properties put together, a house at the front, and a more palatial residence to the rear.

When the member of the Slitheen disguised as a policeman turns up at Mickey's flat, and starts to unzip his forehead, the word "Salford" can be clearly seen graffitied on the wall behind him. Salford is the city in which Christopher Eccleston was born.

It's not strange to U.K. viewers that Mickey would have a cupboard full of jars of pickled onions, pickled cucumber (known as gherkins, as delightedly exclaimed by Jackie Tyler) and pickled eggs. These are staple garnishes for fish and chips, and anyone on a meager budget would consider it prudent to have a few jars in the kitchen, providing they eat a lot of takeaway fried stuff.

And while we're on vinegar, Hannibal didn't just pour vinegar on rocks to dissolve them, his engineers heated any boulders in their path, and then applied the vinegar, which broke them into more manageable bits that could be moved out of the way.

There's an intentional moment of political satire in the speech given by the head of the Slitheen to the waiting press in Downing Street. He refers to "massive weapons of destruction" capable of being deployed in "45 seconds," a parody of the British Government's 2002 dossier that allegedly claimed Iraq possessed weapons of mass destruction that could be leveled at the U.K. in 45 minutes. The Slitheen plan could therefore be said to be a sarcastic retelling of Britain's case for going to war in Iraq.

https://www.youtube.com/watch?v=rrnsd43Lkvw

Trinity Wells—the American news reporter seen from New York—is one of only two characters to appear in Doctor Who, The Sarah Jane Adventures and Torchwood. The other is a French news reporter that was never given a character name. Actually, Trinity (played by Lachele Carl) didn't become Trinity until Season Two. At this point she's just billed as "Reporter."

If, as discussed in 10 Things You May Not Know About "Aliens of London," the original intention was to show that the Prime Minister at the start of the story was Tony Blair, then it seems the set designers wished to inform the world that Tony Blair likes Skittles, as he has a little pile of them next to the red phone in his office.

"World War Three" is the first story in Doctor Who that shows the TARDIS with a working telephone.

The chronology of Doctor Who stories in relation to one another is hard to plot at the best of times, but fitting in Harriet Jones's career is particularly fiddly. If you start by saying that she became Prime Minister in 2006 (the year these events took place), and ran successfully for three terms (each of four-to-five years), as claimed by the Doctor, that means the events shown in "The Christmas Invasion," during which she is ousted from office (again by the Doctor), must take place at some point between 2014 and 2021. And the arrival of her successor Harold Saxon comes even later than that. It is best not to think too hard about this sort of thing, as you'll give yourself a temporal migraine.

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