The Heiress by Jude Deveraux

An impoverished Norman knight, Jamie Montgomery, is assigned to escort Axia Maidenhall, the Lancaster heiress, to her betrothed. But Axia is bent on enjoying her last moments of liberty before her contractual marriage takes place. Suddenly, Jamie realizes that he is falling in love with this beauty, and he must contrive a daring plan to win her freedom and her defiant heart.