It was sinister. It was exhilarating. And by the Face of Boe, Doctor Who finale starter World Enough and Time raised some head-scratching moments. Specifically, 13 head-scratchers, some of which we might be able to make some sense of...

1. Is the Doctor’s name really Doctor Who?

“I grew up with [The Doctor] and his real name is Doctor Who.” It might only have been a joke from Missy, but this small piece of dialogue ignited a firestorm throughout the Whoniverse. Why? Because certain fans will swear that although the show is called Doctor Who, the lead Time Lord’s name is actually The Doctor. 

Only maybe it's not. Showmakers, both of modern and old Who, haven’t formed a consensus. It's simply not clear what's canon and what can be skimmed over – and let’s face it, that's very Doctor Who. 

Read more: We discuss the fascinating history of the debate here – and get Steven Moffat's thoughts on the whole thing. After all, it was him who put the cat amongst the pigeons again...

2. Was The Doctor ever a woman?

Yes, it’s entirely possible for a Time Lord to change gender during a regeneration, hence the speculation that Capaldi's replacement could be a woman. But is it possible that The Doctor’s already led a life as Time Lady? 

During the episode’s earlier flashbacks The Doctor says this to Bill about his years in the Time Lord Academy with the Master: "She was my man crush... I think she was a man back then – I'm fairly sure that I was too..."

Another throwaway joke? Or something more meaningful, a clue that one of the Doctor's previous regenerations – before William Hartnell’s ‘First Doctor’ – was a woman? Thanks to the character’s mysterious history it’s unlikely we’ll ever know for sure...

Read more: there is one episode from the classic era of the show that leaves the door open...

3. What experience has Bill had of Missy?

During the rooftop flashbacks, Bill confessed her true feelings about Missy to The Doctor: “She scares me, really scares me.” But why?

Granted, The Doctor’s probably dropped some hints about Missy’s evil deeds to Bill, but since he's trying to paint her as good at good at heart and willing to change, it’s unlikely he divulged the full extent of it. Plus, if Bill had learnt about Missy’s past dealings with the Cybermen then she should have twigged that the ship’s ‘conversion theatres’ had something to do with the robotic monsters.  

Her only prior experience with Missy is witnessing her crack out a few fun tunes on the piano and while, granted, Missy comes across as a tad unhinged, is that reason for Bill to be terrified of her? We would call out Bill for being a great big judgmental Judoon, but she’s probably got bigger problems on her mind at the mo...

4. Do black holes really slow down time?

Yes, they really do. And it’s awesome.

Thanks to the power of time dilation it is indeed possible for the bottom part of the 400-mile-long ship to be living in a slower timeline than the top. 

Why? Well, basically, the larger an object’s gravitational force, the more it warps spacetime. That means the closer you are to it, the slower your timeline is compared to elsewhere, even if it's only by microseconds. And black holes, well, they’ve got a massive gravitational force.

Want to know more about this timey-wimey wonder?

Read more: We spoke to a couple of experts to provide a full explainer that you can read in minutes (depending on whether you’re falling down a black hole or not). 

5. How long was Bill chilling with The Master?

The Doctor never finds out how long Bill was actually waiting for, but fortunately the clocks simultaneously showing how much time has passed at either end of the ship mean we can work it out. Unfortunately, there’s actually a continuity error between the two occasions when we see the clocks.

The first time we see them, just after Bill comes out of her initial round of Cyber-surgery, gives the relative times as….

  

However, later in the episode (when Bill already has her Cyber chest plate installed and is seen mopping the floor) the clock for floor 0000 is actually 17 seconds further back in time…

 

But, ignoring the second set of clocks, it’s still possible to work out how long Bill’s been down there. By our calculations, the clocks are moving at a rate that means for every one second spent on floor 0000, 149109.096 seconds (or about 2 days) go past on floor 1056. So assuming the Doctor was on the top level for 10 minutes (as Nardole estimates), Bill has been waiting in the lower decks for 2.8 years!

6. Is Bill really a Cyberman forever?

At the end of the episode we saw poor Bill in her new Mondas Cyber-suit, seemingly converted into one of the show’s oldest monsters. But could she be transformed back into a human? 

Previous episodes have shown cyber-conversion can be reversed, providing the human wasn’t fully converted. For instance, James Corden’s Craig Owens in episode Closing Time (2011) was un-Cyberfied after the Eleventh Doctor interrupted the process, and Matt Smith’s Doctor reversed his own partial Cyber-conversion in Nightmare in Silver (2013). And at the end of World Enough and Time we saw Bill's tear-filled eye through her Cyber eye-hole, so at least some part of her, both physically and emotionally, remains.

 

In the trailer for the next episode, we hear Bill’s voice saying “we’re not going to get out of this one are we?” Granted, it’s not the most comforting message, but it’s definitely spoken in Bill’s un-Cyberman voice.

Could this be from another flashback? Does she survive a reverse conversion? Or could the Mondas Cybermen finally get over their habit of randomly stressing words

Who... knows.

7. Is Pearl Mackie going to leave Doctor Who?

Whether she ends the series as Cyber-Bill or not, the latest Doctor’s companion could leave the Tardis for good next episode. Pearl Mackie, who plays Bill, has been dropping a lot of hints about her future on the show. Unfortunately they’re all suggesting different things.

Firstly, Mackie recently hinted that she hoped to stay on, which probably wouldn't work if she was killed in the finale (then again, this is Doctor Who).

However, the day before gifting us that clue, Mackie said in a live Facebook Q&A session that there would be a “lot of endings” in the finale. Will one of them be an ending to Bill Pott’s story? A show insider reassured RadioTimes.com this comment wasn’t confirmation either way, so looks like we’ll have to wait until Saturday to see.

8. Did the Master create the Cybermen?

Although the Genesis of the Daleks has been fully explored, the exact origins of the Cybermen haven’t been played out on-screen. Well, we say Cybermen, let's make that specifically Mondasian Cybermen and their numerous subsequent upgrades, as opposed to the Cybermen created on a parallel Earth by business tycoon John Lumic (we repeat: this is, after all, Doctor Who).

The Mondasian Cybermen appear in just one Doctor Who story before World Enough and Time, William Hartnell’s Doctor Who swan song, 1966's The Tenth Planet, in which they explain that top scientists on their planet of Mondas have been gradually strengthening their weak bodies until they are now almost entirely cybernetic. Their brains are basically human expect for the fact that they've had pesky emotions removed, which are also considered a weakness.

We also learn in audio story Spare Parts (2002) that “The Central Advisory Committee of Mondas”, a group of 20 Mondasians, were the ones to start off the Cyber-surge.

Could The Master be behind the Committee? Or has he meddled with history to supersede the original Mondasian history and create what he calls “The Genesis of the Cybermen”? Or both? Either way, it’s probably bad news for The Doctor. 

9. What is The Master’s plan?

Okay, spawning the Cybermen and transforming The Doctor’s companion into a machine is a good start to an evil Master plan, but there’s probably more to come.

We're thinking about Missy here – it’s likely The Master resents how close she’s gotten to The Doctor. As The Master says when he reveals himself to his next incarnation: “I’m worried about my future”. So, is his end game getting Missy to play for the bad guys once more?  

10. Will Missy help The Master or The Doctor?

Her lifelong frenemy or her former self: who will Missy side with? Sure, The Doctor had seemingly tamed the rogue Time Lord, but can she ignore the devilish Master on her shoulder? After all, she seemed pretty smitten with “the ex” at the end of the episode.

The trailer for the next episode hints this will be a key theme, with The Doctor pleading (probably to Missy) “Stand with me. It’s all I want.”

And it looks as if she may be persuaded: there are several shots of Missy standing alongside Capaldi’s Doctor, with their screwdrivers/umbrellas outstretched. The only problem? Despite his cries of “I’LL NEVER STAND BY THE DOCTOR!” The Master is indeed standing by The Doctor and Missy. 

Could the Cybermen have turned on The Master forcing all three Time Lords to combat them together? Could this be the beginning of a beautiful friendship? Probably not.

11. If Missy kills The Master, will Missy cease to exist?

Imagine it: if The Doctor and Missy team-up and become responsible for The Master’s death then won’t that create an almighty time-tear? Won’t Missy simply disappear as she’s killed her younger self?

Not quite. Remember, if Missy kills The Master then he’ll regenerate into a younger Missy rather than outright die: she wouldn’t be murdering her past incarnation, just giving herself the Time Lord equivalent of a bloody nose. So it’s not necessarily a so-called 'grandfather' paradox. 

And here’s where it gets really exciting. If Missy forces The Master to regenerate then Missy would have always possessed the memory of regenerating at her own hand – the memory of wanting to murder a version of herself. 

This could mean that for as long as we’ve known Missy, she’s harboured this knowledge of self-betrayal, which makes her character infinitely more interesting. Would she try to blame her semi-suicide on The Doctor and be determined to take revenge? Is it an almighty coincidence that the first time Missy reveals herself as The Master incarnate in series eight's Dark Water she’s attempting to take down The Doctor with Cybermen? And, taking this theory further down her timeline, as Missy's character developed through series ten did she quietly accept that it would be a good thing to stop her past self at whatever cost?

No doubt, it would be a remarkable (not to mention very confusing) character arc. However, if Missy – the future version of The Master, remember – has always had memories of the events in World Enough and Time then why didn’t she recognise the camouflaged Master? Surely she’d remember donning a prosthetics disguise for 10 years? Well if she really was planning on destroying her former self, she have to fake not remembering him, right? 

12. Was that really Peter Capaldi's regeneration?

At the start of the episode we glimpsed Capaldi clambering out of the Tardis onto a sheet of ice, his hair wild and hands glowing. As his face ignites with regeneration energy the Time Lord screams “No...no....NOOO!”, prompting one question for the audience: did we just watch the beginning of the end?

We know Capaldi will be exiting the show at Christmas and this polar scene would suit the festive theme perfectly. Yet could this just be another part of his drawn-out regeneration? In the finale trailer we see The Doctor’s hands light up with (the now very familiar) amber Time Lord energy.

Are both these simply signs of another huge tease, akin to the regeneration fakeout in The Lie of the Land? Or could this scene be part of a larger arc?

Read more: in this article dedicated that vey question.

13. Were there hints in the episode that the rumours about the Christmas special are true?

You know the ones: the whisperings that Capaldi’s Doc could bang into the character’s first incarnation, originally played by William Hartnell and now by An Adventure in Space and Tim's David Bradley. The theory goes that the Twelfth Doctor teams up with his former self, possibly during the events of The Tenth Planet – Hartnell’s last story and one that the Doctor was largely absent from due to the actor's real-life health issues.

 

In that story The Doctor and his companions travel to the South Pole to battle the original Mondasian Cybermen – the same version of the Cybermen featuring in the most recent episode of Who. And, yes, that polar setting certainly matches the one we see Capaldi in...

 

Could the fan-pleasing fan-theory be true? We’ve got our yellow glowing fingers crossed.

Doctor Who series 10 concludes on Saturday 1st July at 6:30pm