Mitford family to "The Times" journalist Ben Macintyre, as "Diana the Fascist, Jessica the Communist, Unity the Hitler-lover; Nancy the Novelist; Deborah the Duchess and Pamela the unobtrusive poultry connoisseur". The family traces its origins in Northumberland back to the time of the Norman conquest. In the Middle Ages they had been Border Reivers based in Redesdale. The main family line had seats at Mitford Castle and Mitford Old Manor House prior to Mitford Hall in 1828. The sisters achieved notoriety for their controversial but stylish lives as young people, then for their public political divisions between communism and fascism. Nancy and
They Were Sisters from the immediate aftermath of World War I through to the late 1930s. The screenplay was developed by Pertwee from a popular novel of the same name by Dorothy Whipple, published in 1943. "They Were Sisters" features the spouses of both Mason and Calvert; Pamela Mason (billed under her maiden name Pamela Kellino, and playing Mason's daughter despite being only seven years younger) and Peter Murray-Hill. Mason later admitted that he acted most of his bullying, sadistic role with effectively an ongoing hangover as a means of dealing with the frustration he felt from his role and the British film