Pretty spoiler heavy question since it involves the book's end.
Alan Garner's YA novel The Owl Service sees three characters roughly re-enacting a tragic love triangle from Welsh myth.
Alison, the only girl, is clearly Blodeuwedd. From the events of the book we can work out that Gwyn, a working class Welsh boy made good, is the trickster-hero Lleu. Roger, the snobby English prep school boy is, therefore, Gronw.
Roger and Gwyn begin as friends, but as the legend plays out, they begin to hate each other. Roger instigates this, viciously taunting Gwyn about his attempts to climb up the social ladder.
At the conclusion of the book, the two boys learn that to avert the coming tragedy, one of them must put aside their hate. Once this was clear, I had presumed Gwyn would be the one to yield, since in the sense of "justice" he is the injured party: someone who has been abused by life and by Roger's insults and by Alison's rejection.
But it seems he cannot. Instead, Roger takes the step and ends the book in the role of hero.
The only clue to Gwyn's motivation is this:
Gwyn turned his head and looked at Roger. Roger saw the question form in his eyes, and he saw that Gwyn knew.
It is not clear to me what Gwyn "knows" or why it stops him from releasing his hate of the English children. What message, then, does the redemption of the bullying snob Roger and the failure of the striving Gwyn, give to the reader in terms of the social politics of the book?