Lady Mary Beaumaris

Lady Mary Beaumaris (nee Caldicot) is the late mother of Robert Beaumaris and the daughter of the Dowager Duchess of Wigan. She had four brothers, including the present Duke of Wigan, and three sisters, including Lady Caroline Caldicot.

Her mother the Dowager Duchess called her Maria. As all other characters call her "Lady Mary", it can be assumed that "Maria" was a family nickname.