The jacket copy of Leslie Brody’s new biography Irrepressible will tell you that Jessica Mitford, or Decca, as she was nicknamed, was “yoked to every important event for nearly all of the twentieth century.” This is a bit much, but it’s true that Mitford witnessed some of the century’s major events. Even as a teenager in 1932, “using a diamond ring, Decca and [her sister] Unity etched symbols of their political affiliations into the window of the room they shared at the top of the house—Unity drew a swastika; Decca a hammer and sickle.” The Mitford family’s inner turmoil—with most members (