Æthelfrid

 was the Queen of Mercia. It was said that she was a warrior queen, and fought of the invaders from Denmark and Wessex. John Bleak and Tegan Jovanka met her in Derby when Philippa Stone's machine took them to her. When her daughter Ælfwynn was taken back to the 20th century, she questioned Tegan and John. She later asked Tegan to impersonate her daughter. (AUDIO: The Lady of Mercia)

Behind the scenes
's historical counterpart was actually named Æthelflæd.