“Ascension of the Cybermen” paints a bleak picture of the future, in which humankind and Cyberkind have practically wiped each other out. It’s a story of the faintest hope set against the most brutal odds, with the likelihood of a satisfactory outcome diminishing with every new Cyber attack.

It is also the story of a particularly resilient Irish police officer called Brendan. The link between these two stories being kept secret, for now at least.

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

• There are only eleven Doctor Who TV stories in which the TARDIS does not make an appearance, two of which have occurred during the Thirteenth Doctor’s era. The full list is as follows: “Mission to the Unknown,” “Doctor Who and the Silurians,” “The Mind of Evil,” “The Dæmons,” “The Sea Devils,” “The Sontaran Experiment,” “Genesis of the Daleks,” “Midnight,” “The Lie of the Land,” “The Woman Who Fell to Earth” and “Ascension of the Cybermen”.

• Julie Graham – who plays Ravio – is a familiar face to British TV viewers, and should be a familiar voice for Doctor Who fans too. As well as appearing in The Sarah Jane Adventures as Ruby White in “Goodbye, Sarah Jane Smith,” she has made several key contributions to Big Finish audio dramas, including “The Blood Furnace” (as Carolyn) and “Planet X” (as Prime Minister 470). Additionally, she had a key role in the BBC drama Survivors in 2008, which was loosely based on a post-apocalyptic novel by Terry Nation, creator of the Daleks.

• Cybermen are described as being “allergic to gold,” which does a pretty good job of covering the complex relationship they have with this most valuable of elements. Powdered gold blocks the respiratory filters in a Cyberman’s chest, killing them instantly. This led to such developments as gold-tipped arrows (in “Silver Nemesis”), a move by the Cybermen to blow up a solid gold satellite moon of Jupiter (“Revenge of the Cybermen”) and even a pretty effective glitter-gun (“Earthshock”).

The latter story also saw the Fifth Doctor kill a Cyberleader by grinding the gold edge of his companion Adric’s star button into his chest. This makes the Eleventh Doctor’s temporary defeat over the Cyber-Planner in his head by walloping it with a golden ticket (in “Nightmare in Silver”) look a bit feeble by comparison.

• Ian McElhinney – who plays Ko Sharmus – is a human crossover between the worlds of Doctor Who and Star Wars. He appeared as a slightly younger General Jan Dodonna in the 2016 spin-off Rogue One: A Star Wars Story.

• Aside from the moment where Graham finds himself explaining the meaning of the Cockney term “butcher’s hook,” his big slang moment this week is the term “bish bash bosh,” an onomatopoeic phrase describing the sound of rapid blows, delivered impatiently. It appears to have first emerged in the 1960s as a way of expressing a no-nonsense, straight-to-the-point attitude towards task management.

• There’s a moment of pure fan service when the Doctor offers Ryan a humbug from a paper bag, just as her former selves – particularly the Fourth Doctor – used to do with jelly babies. Mind you, Four actually offered a humbug to Gatherer Hade in “The Sun Makers” too, although his never had any extra ginger. And the paper bags speak to a time when sweets were purchased in quarter-pound servings from British newsagents.

• The Doctor asks Ko Sharmus if he minds if she has “a shufti round.” Shufti is a phrase meaning “have a look,” which was taken up by British servicemen who had served in the Middle East, most probably starting in the RAF in the early 1930s and moving to the Army by the start of World War II. It’s based on the Arabic šāfa, meaning “have you seen” or “try to see”.

• Here’s a geeky spot: this is only the second Thirteenth Doctor story to feature the full melody of the theme music in the end credits, including the triumphant “middle eight” section. The first was “The Woman Who Fell To Earth”. All the other ones cut out with a big boom before we get to that bit. Like this:

• And an even geekier one: the Cybermen refer to Ashad as “Leader” (after a certain amount of hostility on his part). It’s noted that the “handles” on his helmet are black, which accords with the color-scheme of every other Cyber-leader since 1975. And also those of Brigadier Lethbridge-Stewart when he is posthumously converted at the end of “Death in Heaven”.

• Graham gives Yedlarmi the affectionate nickname Eeyore, which is, of course, a reference to the dour donkey in the stories of Winnie the Pooh. This is by no means the only reference to the works of A. A. Milne in Doctor Who history – there’s even a spin-off book of Doctor Who poetry by Russell T Davis and James Goss called Now We Are Six Hundred – but did you know that when the Eighth Doctor’s personalities were split into three (in the audio drama “Caerdroia”), his companion Charley Pollard named the most excitable one Tigger and the grumpiest one Eeyore?!

Do you have a favorite moment from "Ascension of the Cybermen"?