The newest installment in Tom Clancy’s Jack Ryan series, Jack Ryan: Shadow Recruit, hits theaters today with Chris Pine stepping into the famous CIA analyst’s shoes, and he makes sure to bring a stylish woman—played by Keira Knightley—along for the ride. Costume designer Jill Taylor gave InStyle.com an exclusive breakdown of Knightley’s looks in the new film. “When Keira and I first spoke, I asked how she wanted to portray this lady,” said Taylor. “She felt that Cathy was a no nonsense practical sort of a girl, almost like a tomboy. No frills no fuss!”

Taylor drew on Keira’s characterization of Cathy, while also being inspired by the actress’ own sense of style, “I just wanted to convey that this character was a practical, intelligent girl, with an inherent sense of who she was, who had more important things to think about, other than the way she looked. Keira wears clothes beautifully, she has an innate sense of her own style, and so it was obvious to exploit that in this film.”

Additionally, Taylor added a sense of old Hollywood and classic style into Keira’s wardrobe, “I have always been a huge fan of Katharine Hepburn, particularly her style, and so looked to her for inspiration, she had a practicality about her, a simplicity of dress, but still always managed to look feminine even wearing pants, men’s brogues, and a simple shirt.” This simplicity of dress was especially essential when picking an important black cocktail dress Keira wears in the film. Taylor went with a beautiful Lanvin dress that filled all the requirements it needed to, “it had to possess the combination of simplicity,  (in keeping with her character) glamour, (it had to tell a story in as much as Cathy wanted to look great, she was coming to Moscow thinking her fiancé Jack was maybe having an affair) and practicality (she had to be able to move in this dress easily, because of all the action work required in the script).” Scroll down to enjoy even more exclusive details on Keira Knightley’s wardrobe. Jack Ryan: Shadow Recruit hits theaters this Friday, January 17.

Keira Knightley Larry Horricks / Paramount Pictures

“This picture of Keira on the bed wearing a grey coat is really the best example of the Kate Hepburn influence. Wide legged grey herringbone Margaret Howell pants, blue silk shirt, tailored like a man’s, oxblood brogues from Tod’s and a Ralph Lauren cashmere coat, very simple and understated,” Taylor explained exclusively to InStyle.com.

Keira Knightley and Kenneth BranaghLarry Horricks / Paramount Pictures

“I think about fifty dresses must have been sourced, and about twenty five made it into the fitting with Keira, all of which she tried on, she’s a game girl!” Taylor shared of the process of picking Keira’s Lanvin cocktail dress. “Interestingly, I had seen the black Lanvin dress weeks before Keira was cast, and had loved it. It remained my favorite throughout the whole process, and I thought Keira looked sensational in it. As soon as she put it on, we all thought this is the dress.”

Chris Pine and Keira KnightleyLarry Horricks / Paramount Pictures

“Clothes are the clues to the character, to help lead the viewer in to who this woman is. Nowadays, it has become about the clothes, it’s a fine balance for costume designers to keep producers, studios and actors happy while trying to keep the character authentic and believable,” Taylor said of her process on this film.

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—Nicola Jones