On a wintry December, a woman clothed in white fled from Oxford Castle. Besieged by her enemies, she took the opportunity of a snowstorm to move undetected through their siege lines, and down the frozen Thames to safety.

This is the most famous incident in the life of Matilda, Empress and Queen of England, featured in countless English stories and legends. But Matilda is much more than that daring escape. She was the daughter of Henry I of England, the granddaughter of William the Conqueror. Betrothed to the Emperor Henry at the age of 8, she had lived in Germany and Italy until the death of her husband, though she retained the title of Empress until her death. Her father made her his heir; and that escape from Oxford Castle was a incident in the war that she waged to maintain her kingdom. She would live to see her son Henry take the throne, and create an kingdom that dominated both the British Isles and France.

With me to discuss one of the most remarkable yet sadly forgotten women of the Middle Ages–or any other age–is Catherine Hanley, author of Matilda: Empress, Queen, and Warrior.