The Crown costume designer Amy Roberts on outfitting the evolution of Princess Diana

The fourth season of The Crown spans the ‘80s and revolves almost entirely — on both a personal and a political level — around two very different women. Emma Corrin and Gillian Anderson join the cast for the latest chapter in Netflix’s addictive royal drama as Princess Diana and Margaret Thatcher, respectively, and both women’s journeys after being thrust into their corners of the royal arena give the season its shape.

Emmy-winning costume designer Amy Roberts, though tasked with dressing the cast for what is arguably fashion’s ugliest decade, had a thrilling challenge in creating the wardrobes for the new characters; “those two women were quite amazing to do,” she tells EW. Though celebrated as a style icon now, Diana Spencer hadn’t found her look yet when she met and married Prince Charles. She begins the season “a young girl, just leading her life like young girls do, in a flat, not particularly fashion-conscious,” Roberts says. “She just kind of looked ordinary. You know, bobbly old cardigans and jumpers and skirts — a bit dumpy, really.” (Corrin agrees: “I was like, are you joking?”)

Her look evolves a bit when she moves to the palace, but “it still wasn’t quite her. It was a little bit old-fashioned and safe,” Roberts observes. The third episode, which is almost entirely Diana-centric, sees her sitting around and waiting for an absent Charles in the lead-up to their wedding day — sometimes roller-skating or practicing ballet, but always looking very girlish, all puffed sleeves and ruffled edges. Wryly titled “Fairytale,” the episode invokes the popular conception of Diana as a sort of doomed Cinderella.

“Ben Caron, our director, had always imagined it like a Cinderella story. There’s even [a scene] with the Queen Mother receiving the phone call that they’ve got engaged, and he shot it with a little mouse scurrying along the wainscot — very Cinderella-like,” says Roberts (who names the Liberty-print skirt and ruffled vest, below, as her favorite Diana look from the season, “just because I love Liberty prints.”).

“All the kind of ‘80s frilled-edged necklines and pearls are very much what she wore, but they are very princess-like,” she continues. “And then it sort of culminates in the wedding dress. It’s almost like a big Walt Disney fantasy, that dress.”

Because “Fairytale” ends as all fairy tales do — with a wedding, and one for which Roberts recreated the most famous gown Diana ever wore, originally designed by David and Elizabeth Emanuel. “It’s not an absolutely spot-on copy of it,” Roberts clarifies. “It’s closing your eyes and thinking, ‘What was that dress like?’ And it was big sleeves, wasn’t it, big puffed sleeves and that big skirt.”

While some costumes on The Crown — like uniforms and ceremonial pieces — demand accuracy, “there’s a mixture,” Roberts says. Familiar outfits like the wedding dress, the llama sweater, and the yellow overalls fall into “that kind of bit in the middle where you can be quite stylized and chic and use your imagination a bit more. I don’t want to actually copy [everything] to the nth degree; I don’t think that’s my job. I’m a big believer in making a big nod at it.”

Diana diehards might have been disappointed the season lacked a John Travolta moment, but the young princess did have two major dance scenes — to “Can’t Take My Eyes Off You” in Australia and, improbably but accurately, to “Uptown Girl” at the Royal Opera House — and Roberts modeled both of those costumes after real historical looks.

The entire Australia trip, in episode 6, “Terra Nullius,” is something of a fashion show for the globally adored young princess, and “when we did that series for the Australian tour, you almost felt somebody else was dressing a doll up,” Roberts says. “It was like designing a dress-up dolly look for each occasion. I always felt very much at the beginning that’s what we were doing, for her.”

As Diana evolves and is forced to steel herself against the growing toxicity of her marriage, though, her Cinderella paper-doll sweetness makes way for some tougher, more active ‘80s silhouettes. “You feel she’s growing up a bit,” Roberts says.

Her unlikely fashion foil is all grown up, however, and dressing with intention from day one. “If you forget the politics and how you view what she created in ‘80s Britain… [Margaret Thatcher] was a lower-middle class girl who kind of amazingly got into this position of power alongside the queen, really. I found that absolutely extraordinary — how her journey, and her clothes, developed,” Roberts says. “As her strength grew, so did her shoulders. In a way, it was like putting on her armor.”

Roberts dressed Anderson, barely recognizable with that rock-solid bouffant, in Thatcher’s signature blues (including, memorably and inappropriately, while hunting at Balmoral), in shades that are refined and intensified as the PM grows into her power. “She gains strength, if you like, and she moves into those blue pleated skirts and soft bows — incredibly feminine, and extraordinarily manipulative about her femininity,” Roberts notes. “And as the era draws on and her power gets bigger… gone are the soft bows, and her shoulders [become] wider, a very ‘80s, sculptured look.”

Diana also finds that period-appropriate structure as she grows into her own personal power — notably on her solo trip to New York in the season finale, where she wears confident plaid skirt suits and one show-stopping evening gown. “Suddenly we begin to see the Diana that we remember, I think, who was extremely glamorous and strong, although there’s all that stuff going on in her private life,” Roberts says of the sequence. “My memory of Diana is being quite a sort of fit, strong girl — you know, it was the era.”

Her final appearance is her fiercest of the season. “We put her in that black velvet dress right at the end,” Roberts recalls of Diana’s double-breasted halter Christmas dress. “The first time you see Diana [is] as that little elfin fairy creature. And then the final shot of her, when she knows, to survive, she’s going to have to fight this extraordinary setup, she’s in black velvet, showing off these powerful shoulders. That, to me, sort of sums Diana up in season 4.”

Season 4 of The Crown is now streaming on Netflix.

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