The Duchess is a period movie, sure, but the period is less Georgian England than Hollywood’s Golden Age, when entire industrial colonies sprung up around movie stars, charged with the work of tailoring and recutting — by hair-makeup-costume; by lighting and production design; by script and mis-en-scene — essentially stable star personae for every new model year. (As-yet-untitled projects used to be referred to as “Spring Garbo” or “Winter Dietrich.”) As the Duchess — Georgiana Cavendish, Duchess of Devonshire, fashion plate and political reformer and hands-on mom — Keira Knightley indeed “completes [her] ascension as the preeminent period film star of the day,” per Film Comment, which is to say that hers is the set of classy cheekbones and third-wave pluck trotted out every in the fall, the boom season for historically set literary fiction, costumiers and British supporting actors.

Yes, you’ve seen this movie before, the movie about the free-spirited, free-willed, free-loving heroine, who is more than merely the woman society would have her be (while also more of a woman than anyone else in society), a conflict generally dramatized, as it is here, by having a protagonist who’s inclined to think, feel, speak and act as women do today, in a movie of people sporting demurely period-appropriate ‘tudes. So here, following an arranged, loveless (natch) marriage, Georgiana uses her avant-garde fashion sense to draw attention to abolitionist politics (character trait that’s established mostly by the things other people tell her about herself, and also be one scene where she cracks up a room with a political joke centered around her hat). Isn’t it ironic, then, that the sensual world she hopes to make with the Whig Party whelp later to become the Earl Grey (Dominic Scott, given some seasonally appropriate rhetoric about change we can believe in, and looking uncomfortable under his wig) is thwarted by the Duke (Ralph Fiennes, bored and diffidently self-loathing, layering a flat character), obsessed as he is with the continuation of the patrilineal line. Agent of social repression that he is, he tells her that for the sake of the children, she must say goodbye — a vaguely Age of Innocence-y gambit, with more of a focus on the family, mother-love replacing the room-shrinking pressure of social convention. Yes, she must choose between affection, fame and family — though it’s impressive how Georgiana, like Sarah Palin, manages to be icon, political agent and supermom, without any visible help from a nanny — unlike The Duchess, which revels in the opulent lifestyles of the rich, famous and aristocratic, while bemoaning their repressive society too.

Opens September 19