Swaddled in whalebone and wigs, Keira Knightley steps into the restricted world of the Duchess of Devonshire, a royal lady popular with her subjects but stuck in an unhappy marriage. If this situation recalls Princess Diana (a descendent of the Duchess's family), so much the better for the purposes of director Saul Dibb and company; this film is eager to draw parallels with the unfortunate Lady Di, as Knightley's unsuspecting girl is married off to the Duke (Ralph Fiennes), a distracted man who craves male sons, and obviously has never thought of women as anything other than a means to achieve an heir. When the Duchess launches her procreative career with a couple of daughters, well, the Duke begins to get nervous--and partners outside the marriage become increasingly appealing. The Duchess serves up lavish portions of Brit-movie staples: costumes (which, in Knightley's case, are nothing short of spectacular), landscapes and gorgeous music (by Rachel Portman). If it falls short in some vague way, perhaps it's because the film is a mostly one-note affair, meaning exactly what it seems to mean at every moment. Charlotte Rampling appears too briefly as Knightley's mother, and Dominic Cooper and Hayley Atwell (from Brideshead Revisited), rising stars both, contribute attractive lures for the principals. They prove the old movie adage: there's a lot to be said for eye candy. --Robert Horton,