The return of Doctor Who is a mere 11 days away, which means there's precious time left for wild speculation before we all sit down to watch the first episode of series 13, which bears the subtitle Flux.


But we here at have got one last little theory for you – and it comes from a recent press launch for the new series.

Speaking to and other press, Yaz actress Mandip Gill reflected on a particularly memorable stunt she filmed for the new six-part series, saying: "In the first episode, there’s a scene in which we’re above an acid ocean. It was wire work. We were quite excited. And then cut to an hour upside-down – I was like, 'My head’s going to explode. It’s not fun anymore. The harness is too tight.'

"We got some really unflattering behind-the-scenes pictures and footage, which I actually just looked at the other day. There’s a whole bit of being upside-down, swinging around, screaming."

Gill explained that she and co-star Jodie Whittaker "got a little competitive" as they each performed this particular stunt in turn. "We had to swing ourselves around. Jodie went first. So you’re on two wires, pushing yourself, pushing yourself... she did really well. And because we’re so competitive, when it was my turn, I went in, and absolutely smashed it, and got a clap – I got a clap off everyone for doing an extra twirl, just because I wanted to out-twirl her...

More like this

"I hope that bit makes it, because it was really painful!"

It's a fun anecdote, but might it actually contain a hidden spoiler? Because in our Doctor Who-addled brains, something clicked when we heard the phrase "acid ocean"...

As fans of the classic 1963-1989 series of Doctor Who will know, the show's fifth ever story – broadcast in spring 1964 – was The Keys of Marinus, a six-episode adventure written by the Daleks' creator Terry Nation which saw the First Doctor (William Hartnell) and his companions embark on a quest across the titular planet Marinus.

The first episode of the story – entitled 'The Sea of Death' – saw the TARDIS land on an island of glass, surrounded by... a sea of acid.

Doctor Who - The Sea of Death (The Keys of Marinus)
Doctor Who - The Sea of Death (The Keys of Marinus) BBC

What's more, The Keys of Marinus is noted in Doctor Who fandom for its unusual structure – unlike most stories which take place in a single location or just a handful of settings, Keys had its main cast move to a different setting in almost every episode. Flux is similarly expected to tell a single story across six episodes, with the Doctor (Whittaker), Yaz (Gill) and new companion Dan (John Bishop) embarking on a series of mini-adventures all linked by a common theme or quest.

Coincidence? Possibly. An acid ocean might just be an evocative idea that Flux writer and Doctor Who showrunner Chris Chibnall wanted to use again, with no ties to The Keys of Marinus. But in a season that's already incorporating Sontarans, Cybermen, Weeping Angels and more, we're not prepared to totally rule out another nod to the show's past with a return trip to Marinus.

Only a week-and-a-half to go till we find out for sure. Put us out of our misery, Chris...

Check out the official Doctor Who: Flux trailer below:


Doctor Who will return to BBC One on Saturday 31st October. Looking for something else to watch? Check out our TV Guide or visit our dedicated Sci-fi hub.