In a surprise move the BBC have announced that John Simm is returning to play the Master in Doctor Who, more than seven years since we last saw his villainous Time Lord alongside David Tennant’s Doctor in 2009/2010 two-parter The End of Time. 

However, Simm’s return comes with more complications than the average Who baddie comeback. As with the Doctor (currently played by Peter Capaldi), there are multiple incarnations of the Master, with Michelle Gomez’s gender-swapped Missy (aka the Mistress) portraying the character since 2014 – so how could we be seeing Simm’s version again? 

To answer this burning question, some fans have suggested Simm’s return means Missy isn’t the Master after all, and is in fact fellow Time Lord baddie The Rani – but unless Moffat’s comments about the actors playing “the same role” is a huge bluff to hide a massive and unnecessary rewrite of the series, we’d say the truth is far simpler, and a staple of Doctor Who.

Time travel.

As suggested by Simm himself in the announcement of his return, the Master’s comeback will almost certainly be accomplished by the series visiting the character at an earlier point in his timeline.

“I can confirm that it’s true, thanks to the power of time travel I’m back,” Simm said.

The first appearance of John Simm's Master in Doctor Who series 3

However, when exactly we’ll be visiting the Master is less clear. The last time we saw Simm’s Master he was being teleported back to Gallifrey with some nasty Time Lords and was then absent from the series until he’d become Missy. So one explanation for Simm’s appearance would be that we’re going to finally seeing this regeneration, which occurred off-screen between series and remains a mystery to this day.

This could also explain why Simm’s involvement has been able to be kept such a secret for so long, with the filming of a short regeneration sequence achievable on a closed set with a smaller crew. Doctor Who has some form with this sort of thing after bringing back Eighth Doctor Paul McGann for a surprise Day of the Doctor prequel in 2013 (which saw him regenerate into John Hurt’s War Doctor), so it’s not too hard to imagine them similarly filling in the blanks for the Doctor’s nemesis.

There’s also always the possibility that that we’re instead visiting Simm’s Master at a completely different point in his timeline – perhaps during the 10 months he wreaked havoc alone on Earth in 2007’s The Sound of Drums – but a sneak peek at the Simm’s return RadioTimes.com saw at a screening earlier this week saw him closer in appearance to his later End of Time appearance, when the character had dyed blonde hair instead of his original brown. So it seems more likely we’re seeing the Sixth Master towards the end of his life, perhaps for one last goodbye. 

John Simm as The Master in The End of Time part 1

On the other hand, it could be that the Master’s return is much more significant to the new series. In the BBC press release Steven Moffat said that Simm’s and Gomez’s versions of the character will be “face to face” in the new series, suggesting that instead of a simple regeneration flashback we’ll be seeing an evil team-up the likes of which the galaxy has never witnessed.

While episodes including multiple Doctors have been part of the series for decades (most recently in 50th anniversary special The Day of the Doctor), this would be the first multi-Master story outside of audio dramas by Big Finish, and a new benchmark for the series. A bigger storyline like this would make the secrecy surrounding Simm’s return all the more impressive, and could therefore be a clue that he’ll appear towards the end of the series (which has only been filming in recent weeks, making an earlier leak less likely). 

That's perhaps backed up by a recent tweet from Rachel Talalay, who is directing the two-part finale. Reacting to the confirmation of Simm's casting, she posted "Oh yeah. Be afraid". Yes, that might just be a Doctor Who fan who's excited about a returning character. But it could also mean she has first-hand knowledge of just how afraid we should be, and why...

Of course, just how long this “face-to-face” interaction between Masters past and present will last, and what form it’ll take, will remain a mystery until later in series 10 – it could be that we’ll see them briefly interact before Simm regenerates at the end of the episode, like John Hurt’s Doctor at the end of the 50th anniversary special – so until more information is released, we’ll all have to remain in the dark about how this version of the Master came to be back in business.

But whatever the truth, we’re sure that Doctor Who is close to bringing us one of the most exciting episodes to date. Here’s hoping for some Master-full storytelling. 

Doctor Who returns to BBC1 on Saturday 15th April at 7:20pm