The Conqueror by Heyer Georgette

William the Bastard, base-born son of the Duke of Normandy, must fight the King of France to regain his Duchy. Spurned in love by the Princess Matilda, the fighting Duke dares to take a whip to her in her own father’s palace, before making her his bride. William the Conqueror sails to England to claim the Saxon King’s crown and sceptre for his own.