Steven Moffat has said that calling Peter Capaldi’s incarnation the ‘Twelfth Doctor’ is wrong.
Speaking in SFX magazine #251, Moffat said: “I’m just going to throw this continuity grenade back at Doctor Who fans and say, ‘You are all wrong!’ He has never called himself the anything-th Doctor in the show.
“If the Doctor was a real person and walked in here, and you said, ‘Which incarnation are you?’ he’d have to think, just as you’d have to think about how many houses you’ve lived in. He never thinks of himself as a numbered Doctor. The Twelfth Doctor means the twelfth actor to have played the lead in Doctor Who. That’s all it means. There is no such character as the Twelfth Doctor and never has been.
“It’s a long time into the show before any such nonsense ever comes up. It’s purely us lot, us fans, wittering on about calling him the Third or the Fourth Doctor – which is actually quite an unpleasant thing to do. It doesn’t feel right at all when you type that. I had to do that for the [50th Anniversary] special. It was the Tenth Doctor, the Eleventh Doctor, and it felt like a betrayal, in a way. But what else could you do?
“Out of curiosity, I looked at what they did in ‘The Five Doctors’. They didn’t number them at all. Do you know what they called them? The Hartnell Doctor, the Pertwee Doctor…”