Seriously! The British Isles have been hit by one wave of invasion-then-assimilation after another; none of those populations, to the best of my knowledge, got hit by a ray of pure saintliness in the interim.

Also, more broadly, I'm all in favor of historical fiction that explores the tensions and ethnic/cultural divisions within society at a time, but ideally while remembering that, you know, humans are humans! Structural inequality can be extremely one-sided but the moral distribution of individuals is not! Especially individuals who belong to more or less the same culture and class, even if one of them is half-Saxon or whatever! Grump grump grump.