Margaret Pritchard

Lady Margaret Pritchard was the mother of Gwendoline and the wife of Sir George Pritchard.

Josiah Samuel Smith took their home, Gabriel Chase, and removed all knowledge of Lady Pritchard's relationship with her daughter, whom Smith made his ward, while Lady Pritchard became Smith's housekeeper.

When she began to realise the truth in 1883, Light — the alien being who had recently awoken — turned Gwendoline and her mother into stone statues, since he hated change. (TV: Ghost Light)

Behind the scenes
The character's first name comes from the novelisation, and is never used on-screen.