In the latest trailer for Doctor Who’s upcoming tenth series (which, to be honest, you’ve definitely seen by now), one of the most interesting moments is also one of the briefest.

In shots towards the end of the trailer, Matt Lucas’ part-time companion Nardole is tossed a sonic screwdriver of a familiar design – the version of the tool used by Tom Baker’s fourth Doctor – which he then goes on to use in various situations. Maybe the Doctor didn’t trust him with a newer model…

Anyway, exactly why Nardole is given the sonic (and by whom) remains a bit of a mystery, but its inclusion in the series is the latest in a line of weird retro inclusions that could have a deeper significance for the final episodes of Peter Capaldi’s Twelfth Doctor – or could just be a bit of horsing around by the production team.

The most notable example of these throwback classic Who elements comes in the form of the Mondasian Cybermen (see main image), aka the first ever version of the cyborg villains who appeared in original Doctor William Hartnell’s final serial The Tenth Planet. Over the years the costumes for the Cybermen advanced greatly, but Capaldi apparently retained a fondness for the original design, which goes some way to explaining their inclusion in series 10’s upcoming double-bill finale.

However, it is still odd for the series to include such a deliberately outdated design, with the Mondasian Cybermen costumes undergoing none of the revamping we’ve seen for the return of other classic monsters like the Ice Warriors, The Sontarans or even David Tennant favourite the Zygons. What makes them different?

This seems all the more confusing when you consider the possibility that another classic Who foe might be making return in their less-than-modern costuming – android Dalek enemies the Movellans, who eagle-eyed fans think they might have spotted in one of the trailers. 

Here’s what they look like for reference… 

…and here’s where people think they can see them in the trailer, facing off against their traditional tinpot foes. Spot the hair and the hand-gun?

Another slightly odd classic design potentially returning, there.

Of course, behind-the-scenes reasons for all these retro elements’ inclusion are pretty obvious. Showrunner Steven Moffat is leaving this year with star Peter Capaldi and, as both are notorious fans of classic Who, they may just be taking their chance to indulge in a bit of nerdy fun for their final episodes. If you were leaving Doctor Who, why wouldn’t you try and work in a few of your favourite monsters and gadgets in the time you had left?

And as we’ve noted elsewhere, a lot of the new monsters also seem to draw inspiration from recent years of Who, so overall we could see a lot of this as a farewell tour of Moffat and Capaldi’s old favourites.

However, this simple explanation doesn’t mean that there couldn’t also be a reason within the story for the inclusion of all these classic elements – and it might just relate to Peter Capaldi’s regeneration, which will come in this year’s Christmas special.

During the latest trailer, a slightly ominous line is uttered by the Doctor, which seems to echo some of the returning retro elements we’ve already discussed.

"This is the gateway to everything that ever was, or ever can be,” he tells Bill, edited in such a way to suggest he’s discussing the Tardis – but could he actually be talking about something else?

My colleague Paul Jones has previously written about how the return of the Mondasian Cybermen could be an ominous portent for Capaldi’s Doctor – they were indirectly responsible for the Time Lord’s first ever regeneration, after all – and it’s possible that these other recurring classic Who features (along with others we haven’t seen yet) represent the Doctor’s past coming back to haunt him.

If true, this storyline could just be a vague sort of theme (basically the Doctor revisiting his past before stepping into his future), or something more sinister entirely, a plot against Capaldi’s Twelfth incarnation that involves bringing back some of his oldest and deadliest foes in a fitting farewell to the character. 

After all, such an alliance has happened before – in Steven Moffat’s first ever series finale, The Pandorica Opens/ The Big Bang – and with the return of famed Cyberman-wrangler and time traveller Missy (Michelle Gomez) to the series, we could even have a plausible mastermind for the whole shebang.

And of course, when faced with older foes, what better tool to have to hand than an older model of sonic screwdriver? Even if you do just lend it to a guy in a weird little waistcoat…

Now, of course this is also extremely speculative, and it could be that the trend we think we’ve spotted is no more than a coincidental return for some classic Who creations. And frankly, even if it is intentional it seems more than likely that there’s no grand scheme within the story itself to explain why it’s happening – it’s probably just a bit of self-indulgent fun for a pair of old-school Whovians. 

Still, we can’t help but wonder if there’s a larger game at hand here, a way to send Peter Capaldi off with a unification of new and old Who that pays tribute to both his time in the series and his time as a young fan back when the series was still new.

And if that IS the case, we can’t wait to see what other retro surprises series 10 still has in store. It’ll be totally classic. 

Doctor Who returns to BBC1 on Saturday 15th April