Can ye make out that black blob in the distance? Well, THAT is someone wearing a BLACK dress. So could be a wedding dress, or funeral dress, and apparently it looks quite Victorian in its style.
As to who it was, I have no idea, and no one else seems to either, the person was continuously veiled and people on set refrained from using their name.
Apparently from the way they stood and walked, it is confirmed as a woman (it could have been a man) and the suggestions that I've heard of who it is, is as follows:
- The Doctor
- The Trickster
- Miss Evangelista (her name was seen on a trailer for this episode)
- The Black Guardian (with Donna being the white guardian in her wedding dress)
- Astrid (someone who has been noted for knowing things in advance - like there was a sphere in Doomsday containing a black Dalek - has said "She's back. On very, VERY good authority")
You can see the same figure here far away in the distance, wearing a blue parka against the rain and cold...
So there you go... it could also be Elizabeth the 1st since she is due to be making an appearance, and the dress is apparently quite Victorian, but I think this is unlikely as its for Moffat's 2 parter and doesn't seem to fit in with anything else...
Oh! This episode it so confusing!!