In her remarkable new book, Alison Weir recounts one of the greatest and most remarkable love stories of medieval England. It is the extraordinary tale of an exceptional woman, Katherine Swynford, who became first the mistress, and later the wife, of John of Gaunt, Duke of Lancaster. Katherine Swynford's charismatic lover was one of the most powerful princes of the fourteenth century. Their relationship was passionate and ultimately poignant. Katherine was renowned for her beauty; she was enigmatic and intriguing; and some of her contemporaries regarded her as dangerous. Her colourful existence was played out against a vivid backdrop of court life at the height of the age of chivalry, and she knew most of the great figures of the time - among them, her brother-in-law, the poet Geoffrey Chaucer. She lived through the Hundred Years War, the Black Death and the Peasants' Revolt, she knew loss, adversity and heartbreak, and she survived them all triumphantly. Although Katherine's story provides unique insights into the life of a medieval woman she was far from typical in that chauvinistic age. She was an important person in her own right, a woman who had remarkable opportunities, made her own choices, flouted convention and took control of her own destiny - even of her own public image. She was clearly intelligent, with immense ability, and fortunate enough to move in circles where these qualities were valued and encouraged in women. Although she was to suffer a moral backlash she coped brilliantly with the sweeping, and sometimes devastating, changes of fortune that befell her. Above all, perhaps, Katherine Swynford must be retrieved from the footnotes - and set to live and breathe again - because of her key dynastic position within the English monarchy. She was the mother of the Beauforts, and through them the ancestress of the Yorkist Kings, the Tudors, the Stuarts and every other sovereign since - a prodigious legacy which has shaped the history of Britain.