There’s a MASSIVE Time Lord twist in the latest Doctor Who – but what does it all mean?

“You’re probably a bit confused right now,” Martin’s Doctor tells Whittaker’s shortly after the latter discovers her TARDIS buried under a grave at Ruth’s family home.

“That’s my ship […] let me take it from the top,” she continues.

“Hello… I’m the Doctor. I’m a traveller in space in time. And that thing buried down there is called a TARDIS. Time And Relative Dimension In Space.”

Consider our minds blown – because this is no trick. Later, Whittaker’s Doctor scans Martin’s and confirms they are the same person. But it’s a little unclear exactly where Martin fits in, because neither incarnation remembers being the other.

“You’re in my future, not the other way around,” insists Martin’s Doctor.

“I’ve never been anything like you,” Whittaker counters. “Trust me, I’d remember – especially that shirt.”

This marks Martin out as different to the last time Doctor Who revealed a surprise new incarnation, John Hurt’s War Doctor, who was created as a secret regeneration between Paul McGann and Christopher Eccleston’s Doctors. That Doctor was remembered – he was just repressed and ignored over the shame his later selves felt over his actions in the Time War.

Clearly, this new Doctor is something a bit different – though there are a few clues where Martin fits in the timeline. Like William Hartnell’s First Doctor, Martin’s version refers to the TARDIS as her “ship” – a habit that the Doctor eventually lost – and the interior of said TARDIS is closest in style to his classic series version. Also, she’s not familiar with the sonic screwdriver, which first appeared in the years of Patrick Troughton’s Second Doctor.

Later, when it’s revealed the Judoon have actually been hired by the Time Lords to find the Doctor, Whittaker’s version realises that this must be an older version of herself, given that Gallifrey has since been destroyed (twice, actually) and neither the older Doctor or Gat (Ritu Arya) know anything about it. Somehow, she’s completely forgotten one of her lives…

So what could this all mean? Well, we have a few ideas. Clearly, this new incarnation is supposed to be located somewhere around the time of Hartnell’s incarnation. The temptation would be to assume that she comes before him, but the series has suggested Hartnell’s version is the one that originally stole the TARDIS (as seen in 2013's The Name of the Doctor) and got it stuck in the police box shape, which slightly throws a spanner in the works. How did Martin get a police box TARDIS if she came before An Unearthly Child?

Still, a greater mystery is why Whittaker wouldn’t remember this part of her life, which leads us to wonder whether the Doctor – like Ada Lovelace and Noor Inayat Khan in the series’ second episode – has had her memory wiped at some point.

It can happen to Time Lords too, after all – Peter Capaldi’s version had some memories removed in 2015 – though we do have to wonder why such a thing would have happened. Is it somehow linked to the Timeless Child mystery, which the Doctor previously discovered some repressed memories of?

The small girl seen in the Doctor’s vision in Spyfall Part Two (implied to be the Timeless Child) does bear some resemblance to Martin’s Doctor, after all – so was this version of the Doctor actually the Timeless Child? Or did she just find out something about the mystery that led the Time Lords to wipe her memory?

For now, this all remains a mystery. At the end of the episode Martin’s Doctor drops her later self off with a curt “I’d quite like it if you got off my ship now,” and it’s unclear when we’ll see this version in the series again.

But in the meantime, we have so much speculating to do, and we can hardly wait. Roll on more mysteries!

Doctor Who continues on Sundays on BBC One