"He’s a genius. He is a genius actor. That’s not even controversial to say. He’s got a great love of the part. The moment you think of Peter Capaldi and that face in the TARDIS, that works and everybody gets that. He’s going to give us a whole new kind of Doctor. We’ve got used to two brilliant iterations of the younger, more popular Doctor and they have both been superlative. But now it’s time for the old beast to snarl at you for a bit! Sometimes you see that a bit in Matt Smith’s Doctor - he will remind the people around him, ‘I’m not really like this’ - but I think Peter’s Doctor will make that even clearer."
During the Official Doctor Who Celebration in London last weekend, Moffat also offered a few words on what we can expect from Capaldi's first scene in the Christmas Special: "People keep talking about this 'elderly' Doctor that we've cast… he leaps around the place probably more than any other Doctor in that first scene. But that's not how he's gonna play it, he's in a state of post-regeneration madness. It's something we're still working on."
'The Time of the Doctor' is set to air on Christmas Day.