Folville's Law by David Pilling
Available from Musa Publishing November 11 2011.

England in 1326 is a land ruled by the corrupt and inept Edward II and his hated favourites, the Despensers. Threatened by invasion from Edward's estranged Queen, Isabella, and her lover Roger Mortimer, they turn to desperate measures to preserve their precarious hold on England. Caught up in the vicious game of war and politics is Sir John Swale, a landless Northern knight with a dark past, who in the course of serving his masters makes a lethal enemy in the shape of the ruthless outlaw, Eustace Folville.