I imagine this has been asked and answered already though I couldn't find it in my search... I heard a bit in The British History Podcast about how some post-Roman Britons marveled at Roman ruins, believing they were the creation of giants and not simply of the previous civilization. So the structural remains of Rome must have been a mystery to a commoner that didn't know any better about them.

Was there really widespread "forgetting" of Rome? While I'd assume that the Catholic clergy and ruling/trading classes with connections on the continent at least knew of the former Roman glories, and the commoner might know via the Bible that there once was an empire called Rome, did they fully know that that empire extended into the British isles, that those ruins were Roman? If not, what was the explanations of those ruins? And if that memory disappeared, when did it "return" to the commoner?