Montague and Capulet, Percy and Neville, G-Unit and D-Block: Shall the cultural canon’s ageless beefs ne’er be squashed? Tristan & Isolde pits English against Irish in a Dark Ages derby match, with tragic titular lovers caught betwixt. Star-crossed brothers Tony and Sir Ridley of Scott, here producers, call this their “dream project,” which allows them to sub claddagh for sandals in Ridley’s swords-and fetish. Generous feudal lords are they, bequeathing directorial duties to squire Kevin Reynolds, who gave us Costner-in-Nottingham and Costner-with-gills. Middle Ages art direction proceeds as follows: rakishly hung bodices and loads of peat, trés de rigueur. Forgivably anachronistic, because we all get a bit metaphysical sometimes, Isolde (Sophia Myles) reads from Donne’s “The Good-Morrow,” though a somnolent James Franco seems in thrall to his woozy stare rather than his illicit beloved. Myles deserves better, but acquits herself as admirably as one can mired in medieval muck. I dub thee tolerable.