Quite possibly they are Romano-Britons. I'm sure there will be some aspect of "blurred boundaries" a la Gladiator. Slightly OT, but I've been on a serious supernatural horror in wartime binge lately (I just watched Below and R-Point) - do you have anything to rec, by any chance?

Ahaha, no, I know. These people probably didn't even watch the trailer, y'know. Like "article mentions Shyamalan, must destroy!" Even after watching Airbender I still don't think he's like OMG awful, especially because I feel like at least he tries, most of the time. Besides, I love The Sixth Sense and Signs too much. There was a time when he was one of my favorite directors!