The Duchess

Directed by Saul Dibb; starring Keira Knightley, Ralph Fiennes, Hayley Atwell

The duchess is Georgiana, a 17-year-old beauty (Keira Knightley) contracted by her mother, Lady Spencer (Charlotte Rampling), to marry England's most powerful aristocrat, the Duke of Devonshire (Ralph Fiennes). Secretly, the deal entitles Georgiana to a large financial reward once she has produced a male heir for the duke.

When Georgiana hears the news of her future, her face is a mix of delight and awe. The rest of the film examines that love and its brutal consequences for the duchess.

It falls on Knightley to carry the film, as she must carry the mass of wigs on that slender, swan's neck. The much put-upon actress succeeds marvelously here, in the best, most complex and attractive performance of her career.

Although viewers might be distracted by the splendor of her corsets and feathers, her hairpieces towering above her like Amy Winehouse after electric shock therapy, Knightley skilfuly turns Michael O'Connor's exquisite costuming to her advantage.

When, on their wedding night, the thin-lipped, thick-fingered Fiennes asks why women's clothes must be so complicated, she replies: "They are our way of expressing ourselves. You men have so many pursuits; we must make do with our hats and our dresses." It's one of the film's best scenes.

She's excellent, too, when finally learning a young politician (Dominic Cooper) loves her, returning to the misery of her marital mansion only to hear grunts of sex emanating from her husband's chamber.

She's beautiful again, when framed by a brocaded black hood against the duck egg blue upholstery of her carriage, her skin and lips picked out by the single, dirty-pink rose in her hair. We've watched her stomach (Bend it Like Beckham), her pout (Pride and Prejudice) and her shoulders (Atonement) but in The Duchess she acts with her eyes and the result is beguiling.

Oddly, however, the film's emotional power diminishes as its plot progresses, switching between London and Bath, requiring yet another establishing shot of yet another stately pile. It's in these final stages, too, that the film's lack of wider perspective on its historical era begins to look shallow.