The concluding double bill of Doctor Who series ten will bring the Time Lord face to face once more with the Cybermen, but not just any Cybermen – the original Mondasian Cybermen who made their first and last appearance in 1966 story The Tenth Planet.

Of course, until New Who introduced an alternative timeline in which the Cybermen were created on Earth – rather than coming from their own planet, of Mondas – all Cybermen were in a sense Mondasian. But The Tenth Planet is the only time they actually lugged their entire home world with them when they visited, and (spoilers!) it was destroyed at the end of the episode, so in that sense they really are the first and last Mondasians.

They’re also the only ones to have looked quite this spooky, with their ghostly fabric masks and humanoid hands reminding us that there are still something akin to people inside those silver suits.

Peter Capaldi hasn’t even begun his final series of adventures as the Twelfth Doctor, yet we already know that one of his last encounters will be with a very old enemy…

The Mondasian’s return will mark half a century (give or take six months) since we last saw them on screen – but it also seems fitting in a number of other ways. Firstly, the Mondasian Cybermen are the answer Peter Capaldi always gives when asked which classic Doctor Who monster he’d like to bring back. As he prepares to bow out, he’s finally getting his wish and whether it’s due to a nudge from him or is just a thoughtful present form showrunner Steven Moffat, it’s a nice touch.

It’s also worth noting that Capaldi’s first season finale was itself a double bill featuring the Cybermen – 2014’s Dark Water/Death in Heaven. And adding to that pleasing sense of symmetry is the fact that those episodes were directed by Rachel Talalay and written by Moffat, the same pair behind the as yet untitled double-bill which will supposedly be the penultimate episodes for both Capaldi and the departing showrunner.

They’re not the only personnel those two series finales have in common, though. Tucked away at the bottom of the latest Doctor Who press release is another name, Michelle Gomez.

Yes, the Doctor’s maniacal Time Lady nemesis Missy will also be involved, just as she was in Dark Water/Death in Heaven, when she was the mastermind (pardon the pun) behind the return of the Cybermen and an attempt to raise an enormous mechanical army by literally digging up the dead.

Could Missy be the answer to the question of how a strain of Cybermen who were supposedly destroyed along with their planet 50 years ago, have now reappeared? Perhaps she has been dabbling in some time-wimey business of her own to help ease the Doctor towards his next incarnation?

Could there even be another parallel between the series ten finale and The Tenth Planet? Remember, that was the episode that first introduced the concept of regeneration (or “renewal” as it was referred to then) as First Doctor William Hartnell stunned viewers by transforming into Second Doctor Patrick Troughton.

Could the BBC’s insistence that Capaldi’s swansong is the Christmas special be a little white lie? Might he actually regenerate at the end of series ten, perhaps meeting his fate at the hands of his favourite Doctor Who villains? It certainly sounds like something the actor would get a kick out of.

But is it feasible? Steven Moffat says he’s writing the Christmas special, which is unlikely to be the case if it’s the first full outing for incoming showrunner Chris Chibnall and his new Doctor. Of course, history tells us that Moffat’s first rule of the Doctor – “the Doctor lies” – could just as easily be applied to the writer himself when it comes to feeding us red herrings…

Chibnall, meanwhile, says he’s sidelining the casting of the new Doctor while his other show, Broadchurch, runs its course. And, of course, the series ten finale is being filmed now. So it doesn’t add up, does it? Except, what’s to stop Capaldi and co filming everything but the regeneration and tacking that on later? Not only would it give them more time to cast his replacement, it would also be a lot less likely to leak in the run up to the big reveal.

Chibnall, meanwhile, says he’s sidelining the casting of the new Doctor while his other show, Broadchurch, runs its course. And, of course, the series ten finale is being filmed now. So it doesn’t add up, does it? Except, what’s to stop Capaldi and co filming everything but the regeneration and tacking that on later? Not only would it give them more time to cast his replacement, it would also be a lot less likely to leak in the run up to the big reveal.

At this point, we’re straying into the territory of wild speculation, but whatever the answer, as we head towards the Doctor’s regeneration and Moffat’s departure after nine years in charge, the weight of time, the sense of things coming full circle, of death and rebirth, are strong.

As always with Doctor Who, it will be the end of an era. And the beginning of a new one…

Doctor Who series 10 begins on BBC1 on Saturday 15th April.