Warning: Spoilers for 'The Last Letter From Your Lover' below.

In "The Last Letter From Your Lover," modern-day London journalist Ellie (Felicity Jones) unravels the story behind a secret romance in the '60s. The audience sees flashbacks of missed moments between dashing reporter Anthony O'Hara (Callum Turner) and unhappily married Jennifer Stirling (Shailene Woodley). But it's in the pivotal scenes that costume designer Anna Robbins enhances the slow burn — or high tension — through a stunning wardrobe. 

When Jennifer resists kissing Anthony for the very first time, she tentatively approaches his hotel room (to then run off) in a divine Eau de Nil brocade dress with an alluring side and back cut-out (below). Later, when he suggests running away together, telling her she's "wasted in the life" she's living, Jennifer, understandably, turns and flees, revealing a voluminous bow and gorgeously draped pleats billowing out behind her with her berry ensemble (two below). "The back view is just as important as the front view," says Robbins. 

Of course, the two-time Emmy nominee has costume designed plenty of glamorous period wardrobes, including the "Downton Abbey" series and both films.

Jennifer Stirling (Shailene Woodley) 

Jennifer Stirling (Shailene Woodley) 

To portray Jennifer's restrained and dissatisfied society wife, married to the sneeringly bland Lawrence (Joe Alwyn), Robbins looked to the "fashion plates" of the era and issues of Vogue from 1965, '66 and '69. "Her whole lifestyle was based around being a wife and dressing correctly for every occasion and never really being completely free," says Robbins. "It's that sense of everything being meticulously put together, so that the coats are matching the dress and we've got gloves to go with hats... " On the sun-drenched French Riviera, where Jennifer first meets Anthony, for example, and back home in chilly London, she wears monochrome and color-blocked palettes, with elegant scooped necklines, pencil skirts and boxy boats, in perfectly coordinated ensembles. 

Anthony (Callum Turner) and Jennifer in one of her meticulous outfits, featuring the coat with the stunning back.

Anthony (Callum Turner) and Jennifer in one of her meticulous outfits, featuring the coat with the stunning back.

Robbins' color palette for Jennifer delineates not only the jumping timelines, but also the character's hopes and spirits, frolicking about the South of France with Anthony and then juggling real life with Lawrence/Larry at home. "You've got pink, yellow and blue in the Riviera and then, when you bring it back to London, you've got such a dark aubergine and the chartreuse, the dark greens," says Robbins. "She's happy in the Riviera." 

During a seaside dinner party, Jennifer maintains her composure and resolve in a custom-made pink chiffon sheer-sleeve cape gown, despite being condescended to by Larry ("my wife considers anything but the pages of Vogue unworthy of her attention") and catching a sloppy drunk Anthony dismissing the society wives. "I just wanted a really specific color to offset the inky, inky night sky, the tones of the villa and the lighting with the gents in their white jackets," says Robbins, who took inspiration from a flowing Coco Chanel-designed dress in the 1961 French-Italian avant-garde film, "Last Year in Marienbad."

For a romantic sailing trip with Anthony, Robbins found a vintage yellow dress with white seashell-like beading embellishments on the bib (below). "It pretty much fit like a glove when we put it on Shailene," she says. "You tend to do a fitting and see what's working and then start visualizing where these things might fit into the script. Straightaway, it felt like the yacht moment was the time for that dress to be worn. You're against the blue of the sea and the sky." 

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Jennifer and Anthony, living the life on the French Riviera.

Jennifer and Anthony, living the life on the French Riviera.

Robbins used a mix of custom-designed pieces (like a pale-blue coat and pillbox hat, with delicate matching patterned trim, for a frantic run through the rain) and authentic looks '60s, including designer gems from London mainstay William Vintage. "I was looking at Dior and Balenciaga and Lanvin," says Robbins. 

She points to a cream-hued "amazing Courrèges coat" which Jennifer wears with a dark green fedora, as she reads Anthony's letter pleading with her to run away with him. A Dior piece "with a great draped back with a bow" served as an inspiration for a sexily modest bespoke black tunic dress with a cropped jacket which fastens at the back. "In 1969, when she bumps into Anthony on the street and faints, and then she's in the hotel room and and he's helping her dress, that's what that dress is," Robbins says. "Just looking at the beautiful couture construction of the pieces of that time." Jennifer wears actual vintage Dior — a houndstooth cowl-neck short-sleeve top and panel-front skirt — for her thwarted attempt to leave Larry (below). 

Jennifer in vintage Dior.

Jennifer in vintage Dior.

For all of Jennifer's perfectly accessorized '60s outfits, Robbins used mostly vintage bags and gloves, plus a mix of retro and custom jewelry. "We did use Ferragamo shoes, which can can be a brilliant match for the '60s, like slightly square toe and square heels," she says.

But the costume designer points out that Jennifer's streamlined, mid-'60s wardrobe is actually more reflective of the late-'50s in silhouette and spirit. "We see that Carnaby Street '60s vibe, but through her car window," Robbins says. "She's observing that, but she's not part of it. The world she inhabits this is still one foot in the '50s." 

The unrestrained swinging '60s is most represented through costumes in contemporary times — especially as seen on Ellie, who discovers Anthony's letters to Jennifer in the newspaper archives, managed by nerdy-hot Rory (Nabhaan Rizwan).

Ellie (Felicity Jones), in Jennifer-reminiscent houndstooth and '60s Burberry jacket, and Rory (Nabhaan Rizwan).

Ellie (Felicity Jones), in Jennifer-reminiscent houndstooth and '60s Burberry jacket, and Rory (Nabhaan Rizwan).

"Had Ellie been in the '60s with Jennifer, she'd have been living the life that Jennifer wished she was living. She's free and liberated," says Robbins, who also used details like classic houndstooth textures to connect the two. "Actually, we put more typically '60s prints and patterns into the contemporary section, rather than the '60s. We've got Liberty prints on Rory. It's more organic prints and it feels a bit more haphazard, layered and a bit freer."

To illustrate Ellie's "Diane Keaton meets a French chic-Scandi cool vibe," Robbins infused actual '60s vintage into her wardrobe, including a Burberry trench (above), which offered a more relaxed update of Jennifer's pristine neutral car coats. Ellie also wears a pair of black square-toed court shoes from Jennifer's time: "They just set off the real kind of French dandy vibe with a bit of Diane Keaton thrown in," says Robbins. "So rather than them ending up in the 1960s, they ended up in Ellie's wardrobe."

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