Steven Moffat's final episode as showrunner of Doctor Who will hint at the subconscious reasons behind the Doctor's transformation into a woman. At the end of this year’s Christmas special, “Twice Upon a Time”, Peter Capaldi’s Time Lord will regenerate into Jodie Whittaker’s iteration, and incoming showrunner Chris Chibnall will take over from Moffat.

This is a turning point for the overarching narrative of Doctor Who. The last episode to focus on Peter Capaldi’s Doctor is expected to leave “everyone in tears”, before introducing Whittaker as the new incarnation of the series’ immortal protagonist. Outgoing boss Moffat has assured fans that Jodie Whittaker is “already brilliant” in the role. But before he leaves, Moffat is going to touch upon the Doctor’s motivation for changing genders.

Related: First Look At Jodie Whittaker’s Doctor

According to Moffat, the presence of the First Doctor (originated by William Hartnell, but played in “Twice Upon a Time” by David Bradley) will have an impact on Capaldi’s soon-to-die Doctor. Moffat explained this in a new interview with the Radio Times:

David Bradley and Peter Capaldi in Doctor Who Christmas Special

“I suppose at the back of my mind I’ve known for ages the next Doctor was going to be a woman – although I didn’t know which woman – so I was thinking, “Why does he subconsciously make that choice?” Maybe seeing the whole span of his life as a man, seeing himself as the Hartnell Doctor, might make him think maybe it’s time to be a bit more progressive. Looking at how the first Doctor was, he’s hilariously not progressive.”

Moffat went on to stress that, without “being too outrageous”, the First Doctor will come replete with his “1960s political incorrectness” in this special festive episode. Capaldi’s Doctor and the First Doctor will both have to come to terms with their inevitable deaths and face up to the realities of regeneration in “Twice Upon a Time”. Going through this experience will make Capaldi’s Doctor strive to be “a bit more progressive” in his next life.

However, fans won’t get to find out how progressive Whittaker’s Doctor truly is until Fall 2018. Her role in the Christmas special will be brief, allowing for, in accordance with tradition, only one short post-regeneration scene. It will be more than half a year until Whittaker’s Doctor returns for her first full season in control of the TARDIS. Whether or not she lives up to the “progressive” expectations of her predecessor remains to be seen.

More: How The 13th Doctor’s Outfit Takes Inspiration From Previous Doctors

Doctor Who’s next episode, “Twice Upon a Time”, airs on Christmas Day.

Source: Radio Times