Is Doctor Who still hiding a secret regeneration?

It’s a question we asked ourselves after the first episode appeared to show Swarm rejuvenate his body when he escaped his prison, referring to the process as a ‘renewal’ (similarly to early incarnations of the Doctor) and changing actors in the process (from Matthew Needham to regular Swarm actor Sam Spruell).

The idea of a character ‘renewing’ themselves with energy, changing their appearance AND switching actors just screamed regeneration to us at the time, leading us to wonder whether Swarm was a secret Time Lord (of sorts), or had some connection to the Doctor’s own lost species (who had the power to regenerate before the Time Lords, as revealed in series 12).

Seemingly, this theory was cast by the wayside in subsequent weeks, as we learned that Swarm (alongside sister Azure, played by Rochenda Sandall) was actually a being called a Ravager, with vague abilities over time that could explain his rejuvenation. Perhaps his older appearance was just a result of the millennia he’d spent in prison, and his red-faced look his original appearance restored.

However, this week’s episode of Doctor Who – Once, Upon Time – added a new twist. During the Doctor’s flashbacks to her earlier missions against the Ravagers (where she imagined herself in the place of Jo Martin’s Doctor) we meet the younger versions of Swarm and Azure. Azure looks the same…but Swarm, surprisingly, is already his ‘old Swarm’ self, just as he appeared in the Halloween Apocalypse.

Clearly, this appearance wasn’t the result of years of imprisonment – Swarm did genuinely just look different before his ‘renewal,’ right down to the colour of his skin and the style of the prosthetics on the actor. He was the same skull-like species, but essentially a completely different-looking person.

Yes, his renewal could somehow still be connected to his time powers. But given that Swarm didn’t actually age in the thousands of years since his last defeat (and neither did Azure, who looked the same in both cases – though she may have been placed in a present-day time period) and hadn’t bothered to refresh his appearance before facing off with the Division back then, it seems more likely that it’s a similar process to the Time Lord regeneration seen in the show.

Really, it has us wondering. Swarm clearly isn’t a Time Lord – but could the Doctor be a Ravager? In series 12 finale the Timeless Children it’s revealed she fell through a boundary from another universe, already able to regenerate and change her appearance and personality. Who’s to say one of Doctor Who: Flux’s big twists isn’t that the Doctor has more of a connection to Swarm than she thinks?

Of course, it could be that keeping Swarm’s older appearance was pure continuity – this is how we looked when we first met him in episode one, so that’s how he should look in the flashback – but as you start to pick at the logic of the change, you end up with more questions than answers.

Maybe we’re reading too much into it, but we’d say the mystery of Swarm’s renewal isn’t quite closed just yet.

Read more about Doctor Who:

• Doctor Who: Once, Upon Time’s 8 biggest questions
• Doctor Who brought back another Doctor, and it's about time
• Is Doctor Who's Once, Upon Time a pilot episode for a Fugitive Doctor spin-off?

Doctor Who continues on BBC One on Sundays. For more, check out our dedicated Sci-Fi page or our full TV Guide.