Don de plume

Early ON in “The Duchess,” Keira Knightley as Georgiana Cavendish defends her show-stopping chapeaus as a critical means to express herself. Men use wit; women employ feathers. The new film follows the rise and sad stumble of the 18th century style pacesetter, and while many comparisons of her to Princess Diana will be made, the film really could be considered a prequel to “Sex and the City” -- sans the Manolos, of course. “The character is young and innocent in the beginning, but her confidence builds,” says costume designer Michael O’Connor. “We showed that through her clothes and hats.” Meaning, the hats heightened along with her hubris. The film opens Sept. 19.

“The Duchess is a political patron of the Whig party at this point, and she’s out campaigning,” says O’Connor, who worked with London milliner Jane Smith. “We used the fox tails, vintage ostrich tails and the brushed felt of the hat to represent the blue and orange colors of the party. Those tails would shake if she walked very quickly, which was comical. Plus, she’s acting sly like a fox in this scene, so it worked on that level too.”

“Those enormous feathers reminded me of Yorkshire terrier legs. The look was over-the-top because the idea was that she set the fashion and then moved on. You wouldn’t see her wearing feathers again, but the rest of the women would follow her lead. She understood that the public wanted to see her done up. They expected it of her.”

Shake a tail feather

Upper class

Blue blood

“Keira is quite unassuming-looking in real life, and she becomes more and more elegant in dark colors, which are sensational on her. This is a traditional Gainsborough hat [named for the English portrait artist] in black velvet, and those vintage ribbons from VV Rouleaux in London cost $150 per meter. We couldn’t store this hat in a box because it had such a large back. Keira wanted to keep it, in the end. I don’t know how she’s storing it.”

Brim and proper

“In this picnic scene, the hat had to be more rural-inspired and less frivolous. The duchess wants to stand out, but she shouldn’t be gauche. The idea is that the aristocracy wear these straw hats so they look like they’re out walking in the sun. Of course, they aren’t. The hats are two feet in diameter, like giant plates.”

Birds of a feather

“We created all the hats, and there were 30 just for Keira. The hats and dresses always had to coordinate with the harmony of each scene. The biggest challenge was to work with a lot of pastels and neutral colors. We tried to be restrained. Here, you can see that her daughter wants to wear a similar hat. It’s like when a girl tries on her mother’s shoes. The duchess looks like she has it all, but her life was quite tragic.”

-- Monica Corcoran