In all the excitement about Jodie Whittaker’s upcoming debut as the Thirteenth Doctor this Christmas it’s easy to forget that we have so much to enjoy before her first scene, with a whole hour-long episode written by departing showrunner Steven Moffat set to unite Peter Capaldi’s Twelfth Doctor with his very first incarnation (played by David Bradley in imitation of William Hartnell’s original 1960s performance).

And now Bradley has shed some new light on what fans can expect from the upcoming Twice Upon a Time, which apparently sees both version of the Time Lord on a very similar emotional journey.

“It brings together these two Doctors, who are both going through a personal crisis about [whether they should be] regenerating, or just ending it all there,” Bradley told the crowd at MCM Comic-con, where he appeared this weekend.

“And they’re both on this parallel journey of doubt and fear and everything.”

And apparently this inner turmoil manifests itself as some tension between the two men, partly because of the First Doctor’s slightly outdated attitudes (as previously hinted by Bradley in an earlier comic-con appearance).

“There’s a bit of conflict between them – ‘I’m the Doctor,’ ‘No I’m the Doctor,’ ‘No I’m the Doctor!’ and so on,” Bradley said.

“And the kind of contrast in what Hartnell’s Doctor brings coming from the early 60s, and Peter’s Doctor, who’s, shall we say a bit more politically correct than the Hartnell version. There’s a bit of conflict there. But hopefully it’ll be funny as well.

“There’s this tension between them, but I think throughout the story a growing realisation that… ‘Hang on, we’re the same person! What’s this about?’”

And as Bradley went on to explain, this more positive interaction between the Doctors was reflective of his own experience with working alongside incumbent Doctor Capaldi, who made an effort to make Bradley feel welcome on set.

“There’s a kind of mutual respect, I like to think, which grows through the story,” Bradley said of the two Doctors. “Reflected in Peter and I’s relationship – we just got on right from the word go. He made me feel so welcome.

“The first read-through was about 30 people sitting round the table, then another 20 sitting on the outer circle, all the BBC heads of department, all the cast, all the directors and costume, makeup.

“And I thought ‘My God, this is quite big, you know?’ It could have been intimidating, but Peter set next to me and he made me feel really at home right from the word go.

“We had a great time together, and it was a great experience,” Bradley concluded. “I hope it won’t be the last time we’ll work together.”

And who knows? If Capaldi could be persuaded to join Bradley, Whittaker and other stars for another multi-Doctor special in the future, maybe they just might join forces once more. We’re pretty sure Mr Bradley would be up for it, anyway.

Doctor Who returns to BBC1 this Christmas