(Photo: BBC America)
The story so far: The Doctor is heading for her final showdown with Swarm, the crystal-faced rotter that just evaporated her adoptive mother. Time is coming unglued, the universe has been eaten by a cloud of fire aimed specifically at the TARDIS and those mysterious tunnels in Liverpool suddenly starting to make a strange kind of sense.
“The Vanquishers” is the final chapter in the saga of the Flux, the thing that makes the last five weeks of edge-of-the-seat excitement worthwhile. And like all the best Doctor Who grand finales, it leaves the Doctor feeling more than a little bit torn.
Here are a few things to bear in mind, the next time you watch:
1. The idea of the Doctor coming face-to-face with a physical embodiment of time has never appeared in the TV show before, but it did come up in some Doctor Who written media, specifically the Virgin New Adventures series of novels. Within the reality of that series, the Seventh Doctor was characterized as Time’s Champion, and he met the personifications of Time, Death and Pain, who were the immortal gods of Gallifrey. 
2. As we can tell from the sign in Williamson’s tunnels, “The Vanquishers” is set on “December 5th, far future two thousand and twenty one!!,” which makes it one of only six Doctor Who episodes that are set on the day they were first broadcast. The others are “The End of Time: Part One” (December 25, 2009), “The Big Bang” (June 26, 2010), “The Impossible Astronaut” (April 22, 2011), “Resolution” (January 1, 2019) and “The Halloween Apocalypse” (October 31, 2021).
3. The timeliness of this story is further underlined by the fact that there’s a “Hands, Face, Space” government banner in the shopping mall in Liverpool. These blue banners were first put on public display in September 2020, to encourage people not to spread Covid-19 at the time. Although Doctor Who hasn’t explicitly referred to Coronavirus per se, the Doctor did send this personal message during the 2020 lockdown, in which she claimed to be hiding from Sontarans:

And this was a whole year before the Flux hit. Isn’t time travel fun?
4. The Doctor offers Joseph Williamson “a Paul Hollywood handshake,” which is a reference British TV viewers will be more than familiar with. Paul Hollywood is one of the judges on The Great British Bake Off, or The Great British Baking Show, as its known in the U.S. Apparently the term “bake-off” is a registered trademark belonging to Pillsbury.
5. Similarly, the phrase “put you on the [very] naughty step” – as said by the Doctor to Prentis - was popularized in the British TV show Supernanny. It refers to the idea, popularized by presenter Jo Frost, that children who are misbehaving should be left sitting somewhere alone, most commonly at the bottom of the stairs. The length of their exile in minutes would be the number corresponding to the age of the child in years. The Doctor, for example, would be on the naughty step for… well, ages.
6. The Doctor’s reaction to meeting herself – “I've got such a crush on her!” – is a subtle nod to episodes in which previous Doctors have encountered a clone of their current self. Ten was delighted to see the Metacrisis Doctor in “Journey’s End,” until he turned out to be a little too warlike. And Eleven was positively cockahoop to meet his own ganger – who was just as pleased to see him – in “The Almost People”. This is in contrast to what happens when the Doctor meets one of their previous incarnations, which usually results in bickering.

7. Diane explains her excellent sharpshooting with three words, “Laser Quest, Fazakerley,” that might seem like a random collection of sounds at first. Laser Quest is fairly well known, but you may not know that Fazakerley is a suburb in Liverpool. It’s name is a compound of Anglo Saxon words fæs (meaning a border), æcer (field) and lēah, (a wood or clearing).
A relevant thing to note, especially in the light of Diane’s skills, might be that Fazakerley was once the home of the Royal Ordnance Factories plant (ROF Fazakerley) during World War II, which made such iconic guns of the British army as the Sten and Sterling submachine guns, and the Lee–Enfield rifle. Not that any of these are used in Laser Quest.
8. Karvanista’s name is worth a second look, especially as the word karva in Finnish means hair or fur. And a karvaniska is (according to different sources) either a hair follicle, or someone with a hairy neck.
9. Commander Stenk has this extremely Sontaran quote: “We must join together to survive this threat against us. Except Rutans. Rutans, you remain hideous scum and must be obliterated.” This is a reference to the great Sontaran-Rutan war, a battle so huge it was thought to have lasted for thousands – if not millions – of years.
References to this eternal conflict are littered through the Doctor’s experiences with Sontar’s finest, including “Horror of Fang Rock,” “The Sontaran Experiment,” “The Two Doctors,” and “The Poison Sky.” The Third Doctor first met the Sontaran Linx, who had been shot down in the 13th Century by Rutan fighters, in “The Time Warrior.”

10. The Doctor brings Prentis/Grand Serpent down a peg or two with a hearty “Whoah! Ego klaxon!” which is, of course a reference to the well-known electromechanical horn – you’ll be familiar with the noise “awooga!” – as used on cars, trains and ships.
The term “klaxon” was actually a brand name, coined by Franklyn Hallett Lovell Jr., whose company bought the production rights, and helped ensure that klaxons were an integral part of all General Motors cars in the early days of automobiles. The word klaxon comes from the Ancient Greek verb klazō, meaning, "I shriek".
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