Ironclad (2011) on Netflix

King John Lackland reneges in 1215, the year the barons force him to sign to Magna Carta, on its parliamentary terms to resume his tyrannical misrule, and raised an army of pagan mercenaries to smash those barons who dare resist again. William d'Aubigny's warrior band, including knight Templar Thomas Marshal and his squire Guy, decides to make a stand in Rochester, a strategic castle to bar the road to London, so they force its lord, baron Reginald de Cornhill, to side with them after eliminating the Danish watchdogs. Captain Tiberius's mercenary band fails for months to make their numeric superiority count during a bloody siege, over which John presides personally, eager to take the castle before French and/or domestic rebel reinforcements may arrive. Baron Reginald's wife Isabel regrets their arranged marriage, enough to nearly-openly lust for handsome crusade veteran Thomas, who however takes his order vows seriously.