Bradley revealed that there would be some conflict between the Doctors regarding their different social attitudes, which are almost a half-century apart:
“What we did emphasise [about the First Doctor] was the old fashioned nature and how he is from the 60s. He goes into the Twelfth Doctor’s Tardis and says ‘it’s a bit dusty around here, it’s in an awful state isn’t it? Where’s Polly? Shouldn’t she give it a spring clean?’ And then Peter’s saying ‘you can’t say that’.
“[The First Doctor] brings all his 60s sensibilities, what’s lovingly called casual chauvinism. He’s just talking [as if] the [companions] are there just to help out, and do the dusting and do all the domestic chores – his attitudes to a lot of things come right from the 60s, so there’s a lot of conflict between Hartnell’s Doctor and Peter’s Doctor about how things have changed in the last 50 years… we had quite a bit of fun with that.”
As you’d expect from a regeneration episode, it seems that Twice Upon a Time will aim for the heartstrings in its final act, which Bradley hinted at in further comments:
“There’s an event towards the end of [the Christmas special] that happens and when it happened, well, we just did a take and neither Peter nor I expected it. There was no CGI involved, it was all happening and we were both almost blubbing by the time that the take ended. I can’t say, I’m not going to say, what it was but it was quite an event and we weren’t prepared for all the things that were going to be going on around us as we were doing our dialogue.
“And as I say to you, we got quite lumpy. They’ve kept that out of the trailer but it takes it all to another dimension…”
Twice Upon a Time will air this Christmas.