Everyone knows about the six flamboyant Mitford girls but in fact there were seven remarkable women in the famous family—the seventh was "Muv," Lady Sydney Redesdale, the mother of the notorious sisters. Too often portrayed as different from them and outside the girl gang, she was really the original and much of her daughters' strong will, self-confidence, and extremism came from her.

Sydney Redesdale was a divisive figure both among her daughters and subsequent biographers. Until their deaths, her girls were still squabbling over what she was really like, their differing views of her persisted for even longer than the political divides between them. Each daughter wanted to control the narrative and they wrote competing novels, memoirs and letters to vindicate their perspective. For Nancy and Jessica, she was a scapegoat. For Unity, Diana, Debo, and Pam, she was a saint.

Biographers have been equally divided about how she should be portrayed. Many wondered how such exceptional children could spring from such ordinary parents, but was Sydney really so "ordinary?" The story of her life at the heart of one of Britain's most famous families is told in full here for the first time and is a missing piece in understanding one of the twentieth century's most complex and fascinating families.