This week’s Doctor Who was an episode of surprises, from the revelation that (spoiler alert) the whole storyline was pretty much just a computer simulation run by some evil aliens to the fact that the story wouldn’t end in this week’s episode, instead continuing into next week’s instalment The Pyramid at the End of the World.

In effect, this means that writer Steven Moffat has delivered a stealth two-part story, with episodes that were previously announced as individual standalones actually a part of a longer serialised story that nobody was expecting – and it’s fair to say he’s been planning a shock like this for years.

“The rule I’ve got is that you won’t be absolutely certain whether a show is going to be a two-parter or not,” Moffat said in 2015, when discussing the unusually large amount of two-part episodes that were included in that series.

While this effect wasn’t quite pulled off in series 8 (early production details and episode titles made clear which episodes were two-parters and which weren’t), it’s fair to say that Moffat’s desire to spring a serialised story on us has been fulfilled this week, and we can’t wait to see how his follow-up next week (co-written with Peter Harness) continues the story of the dastardly Monks.

Assuming, of course, that it really does end there – because if he pulled off such a trick once, who’s to say he won’t try it again right afterwards to create a surprise THREE- part story? Some fans are already speculating that episode 8 (called The Lie of the Land and written by Toby Whithouse) is actually another continuation of the same story, with the “mass delusion” plot of that instalment actually all a part of the Monks’ evil plans to conquer humanity.

If true, this three-part theory could also explain why Michelle Gomez has recently been confirmed to guest star in the episode, with her appearance there capping off the mini-arc started when the Doctor elected to save her life in this week’s episode. Or, you know, she could just be hanging out.

We’re reasonably confident that this mini-serial will HAVE to stop there – episode 9 sees the Doctor and Bill meet Victorian adventurers on Mars, which would be hard to fit into the Monks’ storyline – but hey, stranger things have happened and maybe we’ll see this serialised storytelling run and run and run.

After all, if six-part stories were good enough for classic Doctor Who, who are we to judge?

Doctor Who continues (and continues) next Saturday 27^th April on BBC1 at the later time of 7.45pm