The Twelfth Doctor's farewell tour is set to welcome a number of famous guest performers back to the stage: Michelle Gomez's Missy, John Simm's Master, the original Mondasian Cybermen, the Ice Warriors – and I've already speculated about one or two others who might end up jamming with Peter Capaldi one last time.
In the context of all those comebacks it would seem churlish to ignore the hints being dropped about yet another character – one of departing showrunner Steven Moffat's own creations – the Doctor's wife, River Song.
River is the definition of a Marmite character – many Doctor Who fans love her for her sassy wit, kick-ass skills and deep connection to the Doctor, others find her self-conscious catchphrases and hammy delivery grating and unconvincing.
I am in the latter camp. But there's no denying that many fans would love to see her return one last time – and if Moffat's not bringing her back in series ten, he's certainly being a tease about it.
We first glimpse the Doctor's wife in the opening episode, alongside his granddaughter in one of the two picture frames that have pride of place on the Time Lord's desk in his study at St Luke's University.
Moffat has said that one of the reasons the Doctor is displaying family photos at work is because he sees it as a very human thing to do, which means it makes sense while he's trying to blend in during his enforced stay on Earth guarding whatever or whoever's in that vault (I think we're all pretty convinced by now that it's a who and that the who is an incarnation of a fellow Time Lord).
But given that we've been shown the photo several times as the series has gone on, it's hard to shake the feeling that there is more to it than that – especially since it's been followed up by several other nods to River.
The next one, in episode two, is relatively oblique, but at the same time pretty clear if you get the reference. When faced with an unidentifiable but fishy tasting meal, the Doctor replies "I'm not that fond of fish, except socially", no doubt recalling the hazy karaoke night the Eleventh Doctor and River spent with a character named Jim the Fish. Sadly, we never got to see this play out (although Islands in the Stream was apparently on the jukebox) but it was mentioned by the Eleventh Doctor in The Impossible Astronaut and by the Twelfth when briefly reminiscing with River in The Husbands of River Song (where Jim comes up in a passage read from River's diary).
In episode three, the Doctor and Bill visit 1814 and London's last great Frost Fair – an impromptu party on the frozen River Thames. No, I'm not making a tenuous river/River connection – the Doctor happens to mention in passing that he's been here "a few times" before, and while that's true it will put New Who fans in mind of one occasion in particular from 2011 episode A Good Man Goes To War, when River turns up in full Regency garb and tells Rory “It’s my birthday – the Doctor took me ice-skating on the River Thames... He got Stevie Wonder to sing for me under London Bridge.”
And now the latest reference, a blink-and-you'll-miss-it moment from the trailer for episode six, in which the Doctor slips a Tardis-shaped diary out of his coat pocket.
There are two of these diaries that we know of, one belonging to the Doctor and the other given by him to River, the idea being that they would each keep a record of their meetings and adventures so that they could always keep track of where they were in one another's timelines and therefore avoid the dreaded "Spoilers!"
Occam's razor says the diary we've glimpsed is most likely the Doctor's, so perhaps he's attempting to check something from his past that might be relevant to the events of this episode, Extremis. That might be a little difficult of course, given that the Doctor is currently blind, but maybe he'll ask his faithful man(robot)servant Nardole to read it to him.
But what if it is River's own diary – how and why might the Doctor come to have it? Well, we know that the Tenth Doctor left the diary in the Vashta Nerada's Library following River's death in series-four episode The Forest of the Dead, and that he also uploaded a data version of her into the virtual world contained in the supercomputer there. To get hold of the diary, he'd have had to go back to the Library – perhaps he needed it to compare something with his own version of events – but once there would he be able to resist the temptation to download River's consciousness again (we know from the original episode that it can be contained in a data recorder within a Sonic Screwdriver)?
In that case, perhaps we're set to see the virtual River in action again before the series is out.
Whatever's behind it, there's no denying that the diary is the latest in a series of clues intended to put River Song back on our radars. Whether it's to prime us for her return or is simply Moffat's subtle way of paying tribute to his creation in his last series of Doctor Who remains to be seen.
One thing's for sure, though – if there is still one more page to be filled in River's diary, it definitely contains spoilers...
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