Current Doctor Who showrunner Steven Moffat has been chatting to Radio Times about the show and, specifically, Peter Capaldi. He told the magazine:
"There is something about Peter's demeanour, his eyes, his attitude - he's tremendously bright and that comes out on screen. When you choose a Doctor, you want somebody who is utterly compelling, attractive in an odd way. None of the Doctors are conventionally attractive but they're all arresting."
Moffat added, "Peter is a man in his Fifties but is terribly boyish and young at times," whilst writer Mark Gatiss also commented that Capaldi's Doctor is, "a more dangerous, more urgent Doctor. It has a side of crazy."
Turning his attention to The Day of the Doctor and John Hurt's "War Doctor", Steven said, "I think it's nice for a hero to have a dark chapter, although it's a chapter we will probably never see again because that somehow isn't Doctor Who."