Could one of these former Doctor Who stars be the new companion?
The new arrival in the TARDIS "knows very little" about the Doctor, according to Peter Capaldi - but is that the same as knowing nothing at all?
Peter Capaldi knows who will be joining him in the TARDIS next year, and says he's "very excited" about it.
"We've been doing a bit of work together already," the Twelfth Doctor told Brazilian website Omelete, adding that unlike Clara, whose Impossible Girl status means she "had prior knowledge" of the Time Lord, "now we have someone who knows very little about the Doctor."
So who is this mysterious new companion? There are a lot of intriguing possibilities out there, but I'm going to do my best to narrow it down using a combination of the latest evidence, educated guessing and wild speculation.
Firstly, I'm going to rule out a male companion. Capaldi has already made it clear he’s not keen – “With the best will in the world, I don’t want a bloke, because I’m frightened that they’ll give him all the action” he told us in December – and until there’s a female Doctor, neither am I. The TARDIS needs to represent both sexes.
I'm also going to assume that the new series will follow recent Doctor Who tradition and keep the companion below a certain age, most likely in her twenties. It's a winning formula for a number of reasons that I probably don't need to go into.
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Next, let's consider Capaldi's comment that we're talking about a companion "who knows very little about the Doctor". I may be reading too much into this but it seems to me that a character completely new to the Doctor Who universe would know absolutely nothing about the Doctor, not "very little".
Could this therefore be someone we’ve met before in Doctor Who but who is not yet a major player? It certainly wouldn't be the first time – as Doctor Who fans know, Karen Gillan made a brief appearance as a seer in series four episode The Fires of Pompeii (the same one where Peter Capaldi played a Roman merchant) while Jenna Coleman turned up unexpectedly in Asylum of the Daleks as Oswin Oswald prior to the start of her tenure as Clara.
If the new companion does turn out to be a recurring star or character, there are clearly numerous people we could consider but here are three that I think are the most intriguing and certainly not outside the realms of possiblity.
Marsay, 29, who appeared in 2014 festive special last Christmas, is a favourite of mine. Her character Shona injected some real-world melancholy, as well as some laughs (see above), into proceedings and would be a very human foil for the Time Lord.
While she shared some dream crab-inspired nightmares with the Doctor, she didn’t really get the chance to learn much about him during the episode – in fact, he learnt more about her, given that most of those nightmares turned out to be based on her lonely Christmas Day watchlist (Alien, Thing from Another World, Miracle on 34th Street).
Unlike the rest of those trapped in the dream world, meanwhile, Shona was reluctant to leave, suggesting that her mundane home life is not enough for her, and that she had the kind of adventurous spirit you'd need to jump in the TARDIS and fly off on adventures with the Doctor.
You may not instantly know the name (which could be an advantage in itself) but back in 2011, Holly Earl played Lily, the young girl who enters a winter (kind of) wonderland with the Doctor in another Christmas special, The Doctor, the Widow and the Wardrobe.
Now 23, Earl has since appeared in BBC3 comedy Cuckoo, landed widespread critical acclaim in BBC1 drama Ordinary Lies and is currently starring in Beowulf. And, speaking frankly, she has the kind of good looks that Doctor Who bosses seem to have gone for in recent years.
Despite the fact that her previous Doctor Who outing was alongside Matt Smith’s Eleventh Doctor, Earl has actually worked with Peter Capaldi, too – more than once...
If you grew up in the late 90s you may well remember another Christmas adventure, kids' favourite The Greatest Store in the World. Capaldi played friendly, if suspicious, doorman “Mr Whiskers”, while Earl was part of the homeless family secretly living in the department store he worked at.
She also had a one-off role in The Musketeers, when Capaldi was starring as the evil Cardinal Richelieu. So the pair have some history together, which could well translate quickly into a friendly chemistry in the TARDIS.
The Fresh Meat star (who coincidentally flat-shared with Faye Marsay's character in the Channel 4 comedy) appeared in series eight episode Into the Dalek and her name has been in the mix to become either the first female Doctor or a new companion ever since.
Ashton played soldier Journey Blue – have you ever heard a name more suitable for someone travelling in the Doctor's police box? – and we know the character would be up for the gig because at the end of the episode she asked the Doctor if she could come with him. He refused because he's not keen on soldiers but she did prove herself to be not only brave but also very humane so perhaps he'll remember that and have a change of heart when he's been rattling around in an empty old TARDIS for a while.
Ashton would also make good casting sense in response to those who are suggesting it's time to see a non-white actor back in the TARDIS again.
Whether or not any of the above turn out to be correct, it sounds like it won't be long until we find out for sure – Capaldi said during his current visit to Mexico that the new companion will be "along any minute"...