Le precedenti apparizioni di Capaldi casuali, o... ?

One section is devoted to regeneration, and the fact that it would not be a break with Whovian tradition for the Twelfth Doctor to look a lot like someone the Doctor has already met. In fact Peter Capaldi has been in Doctor Who (as Lucius Caecilius Iucundus in “The Fires of Pompeii”) and Torchwood: Children of Earth, and Steven has already had a chat with Russell T Davies over how this will all work.

He said: “We are aware that Peter Capaldi’s played a part in Doctor Who before and we’re not going to ignore the fact. I’ll let you in on this. I remember Russell told me he had a big old plan as to why there were two Peter Capaldis in the Who universe, one in Pompeii and one in Torchwood. When I cast Peter, [Russell] got in touch to say how pleased he was, I said ‘Okay, what was your theory and does it still work?’ and he said ‘Yes it does, here it is’. So I don’t know if we’ll get to it… we’ll play that one out over time. It’s actually quite neat.”
It will certainly come up should Donna Noble ever make a return to the TARDIS, given that she met Lucius. Steven also points out that the Doctors always arrive with a certain amount of life history already beaten in, and that Time Lords can pick how they look, to a certain extent, a fact that goes back to the Second Doctor’s regeneration:

“The big fun question is, we know that the Doctor when he regenerates, the faces, it’s not set from birth, it’s not that he was always going to be one day Peter Capaldi. We know that’s the case because in “The War Games” he has a choice of face and all that. We know it’s not set so where does he get those faces from? They can’t just be randomly generated because they’ve got lines and they’ve aged. When he turns into Peter he’ll actually have lines on his face – sorry Peter – so where did that face come from?”