Margaret Pollard
From Tardis Wiki, the free Doctor Who reference
Margaret Pollard was the daughter of Lady Louisa Pollard, and sister of Charlotte and Cecelia Pollard. She once helped the First Doctor stop a demon from killing Edward Grainger. (ST: Prologue)
Her elder sister Charley would later become a travelling companion of the Eighth and Sixth Doctorss. (BFA: Storm Warning, BFA: The Condemned)
