Britain’s aristocracy has seen its share of birds in gilded cages. The difference with the 18th century Duchess Georgina Spencer — a predecessor to Lady Di in ways that go beyond a shared surnamed — was that she understood the value of working her plumage. Trapped in a loveless marriage to man whose interest in her extended only to her ability to bear a son — which she only managed after multiple pregnancies — Georgina turned her attention (and her wardrobe budget) to seducing the rest of the country It’s a compelling story, but The Duchess is airless prestige filmmaking, all lavish interiors, telegraphed revelations (one of which is actually accompanied by the sound of thunder) and a force-five musical score. As Georgina, Keira Knightley looks terrific in her various high–fashion get-ups but never really evinces the desperation (or, to be frank, the physical toll) of her heir-making endeavors. As the Duke of Devonshire, Ralph Fiennes looks as pinched and miserable as Colin Firth (or maybe Voldemort).