The ancient story, and recent film, about Tristan and Isolde is one well worth studying. This narrative has inspired poets, composers, and painters over the centuries, leaving us with many different versions of the same basic plot.
But don't be confused: this is not merely a love story. This is an account of the political upheavals caused by the fall of the Roman Empire, and of the beginnings of English national identity. The effort to unite a handful of independent tribes into what would become England, and the struggle between these collected tribes and the Irish, formed the geo-politics of Europe for several centuries. Understanding this story is understanding what England is, how it arose, and what the authentic English identity was prior to 1066. But 1066 is another story.