So Russell has said that fans will not find any clues in the trailer.
He said, “We argued over [the clips used in the trailers] long and hard. There’s an editor called Thomas back in London at BBC Cardiff who put those together. And we went over them twenty-seven times, every time saying, ‘No, take that out, no, take that out.’ I know science-fiction fans are very, very clever. You can show them one character, and if he’s hiding something in his hand, they’ll guess what it is, and if he’s hiding something, they’ll guess why he’s hiding something and therefore there’s nothing at all left that they haven’t surmised.”
He added: “It’s such a literate audience, all you really get in those Christmas episode clips are faces. Literally, we’re just showing you who is in it – we daren’t show any more.”
He has promised that all this being kept in the dark, will be worth it, he finally said, “You’ll have to wait ’til December, I really don’t believe in giving out information too soon.”