Who is Ruby's mother in Doctor Who? All the theories

The Christmas special, which introduced Ruby and her adoptive mother Carla (Michelle Greenidge), opened with Ruby looking for her biological parents with a little help from none other than Davina McCall.

Later on in the episode, Ruby gets bad news about her search for her parents – but it seems the mystery doesn't end there.

In fact, speaking at the premiere of The Church on Ruby Road, showrunner Russell T Davies said: "This one's quite a fable – the foundling on the church doorstep in the snow. That story then continues into the series – we come back to that church.

"There's all sorts of things... there were people in those scenes you don't know were there. There's a lot more to come.”

Now, as Ncuti Gatwa's first full season as the Fifteenth Doctor kicks off with the episodes Space Babies and The Devil's Chord, fans are keen to know more about the mystery.

Who is Ruby's mother in Doctor Who?

At this point, the identity of Ruby's biological mother is unknown. However, it seems we'll find out more this season, with showrunner Davies confirming that Ruby's backstory will have a big role to play.

The only clues we have from the Christmas episode are a brief sighting of a hooded figure when the Doctor goes back in time to the Church, and an intriguing update from Davina when she phones Ruby with the results of her search.

"There's no trace of your mum or dad. I'm sorry, it happens sometimes," Davina says. "If your parents aren't on some kind of database, we can't find them."

"Isn't that unusual though?" Ruby asks. "That there's not a single trace anywhere? Meaning in the whole wide world, my mother's never left a blood sample or anything?"

Of course, there's not much to go on at the moment, but the mystery of it might suggest Ruby's mother is a character we already know in the Whoniverse. Perhaps it's someone who's spent some time away from Earth, meaning they're not on any databases?

After all, it wouldn't be the first time in Doctor Who history that grand revelations have been made about a character's parentage – lest we forget the great River Song/Melody Pond reveal of 2011.

Perhaps Ruby's mother is another past companion or someone the Doctor has known well over the years? That could explain why the Doctor and Ruby kept being drawn to each other at The Church on Ruby Road.

Elsewhere in the Christmas episode, it was made clear that there's more to Ruby's neighbour Mrs Flood (Anita Dobson) than meets the eye, and she seems particularly fond of Ruby. Could she know more than she's letting on about Ruby's biological mother?

Of course, Ruby's adoptive mother Carla is played by the great Michelle Greenidge. Recently speaking exclusively to RadioTimes.com, Greenidge said: "Carla's bond with Ruby is very special, and there isn't anything Carla wouldn't do for Ruby."

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