Johnny Hitchley's mum

A Zygon took the form of John Hitchley's mother.

Biography
In Turkmezistan, Hitchley ordered the Zygons hiding out in a building to show themselves. Instead, a Zygon emerged in the form of his mother. Colonel Walsh ordered Hitchley to kill her, but Hitchley instead asked her personal questions, such as his date of birth and favorite teddy bear as a child. She was unable to answer, but mentally called out Zygons disguised as the loved ones of the other soldiers. Hitchley loved his mother so much that he eventually brought his soldiers inside. Inside, the Zygons killed them. (TV: The Zygon Invasion)