We’re still over a month away from seeing upcoming Doctor Who Christmas special Twice Upon a Time on our screens, but already a few more details are trickling out about what we might expect from Peter Capaldi’s final episode – and the conflicts that arise within it.

Speaking in a special Doctor Who behind-the-scenes documentary called The Finale Falls (a DVD extra on the complete Doctor Who series 10 collection based around series 10 finale The Doctor Falls), episode writer and departing showrunner Steven Moffat dropped a few hints about the upcoming clashes between Capaldi’s Twelfth Doctor and his very first incarnation, played by David Bradley in the style of original actor William Hartnell.

“David Bradley is such a good swap for William Hartnell,” Moffat says in the footage. “He looks so like him, and can so capture that part.

“We could actually have, in effect, William Hartnell returning to Doctor Who – and witness to his great horror what he has become.”

By the sounds of things, then, the First Doctor won’t appreciate his wild-haired, guitar-playing future self, just as Capaldi’s Doctor reportedly objects to his first incarnation’s slightly outdated attitudes. All of this continues the longstanding trend for different Doctors to rub up each other up the wrong way when their paths collide.

According to Bradley himself, the effects are well worth watching.

“The First Doctor meeting the current Doctor – it’s just so way out there!” Bradley says in the footage.

“And I’m glad Steven Moffat thought of it, and wrote such a brilliant story. But it’s something I would never have imagined.”

Speaking more generally about the episode, Capaldi added: “It’s nice to have conclusions. I think it’s nice for stories to end.

“But Doctor Who never ends.”

And even before the series takes a big new step with Jodie Whittaker’s Doctor, it sounds like the current status quo has a great final story to share.

Doctor Who: The Complete Series 10 is available on DVD now, and can be ordered here!