How 'The Crown' re-created Princess Diana's 'revenge dress'

The true scene-stealer of The Crown isn't one character or storyline per se, but the captivating wardrobes of Princess Diana.

Bringing those ensembles to life are the actresses who play Diana throughout the series — Emma Corrin in Season 4 and Elizabeth Debicki in Seasons 5 and 6. While the show's costume designer Sid Roberts never anticipated that her designs would reignite a new interest in the late princess's fashion, as she tells Yahoo Entertainment, it happened nonetheless. (Click here to see more behind-the-scenes images from The Crown.)

"It's really humbling," says Roberts, who alongside her mother, Amy, has designed costumes for the last five seasons of The Crown. Days after Netflix released Season 6, Part 1, which centers on Diana's final days and her blossoming romance with Egyptian filmmaker Dodi Fayed, in November, audiences scoured the internet for Diana-inspired ensembles.

According to data from retailer Boohoo, Google searches for "Princess Diana revenge dress" rose 400% worldwide (1,654% in the U.S. alone), while searches for the blue swimsuit she wore on a yacht, during what would be her last vacation before her death, skyrocketed 850%, marking a 10-fold increase from the same time last year. Meanwhile, searches for Diana-inspired houndstooth suits and the "pink plaid pants," both worn by Corrin in Season 4, rose by 1,079% and 1,037%, respectively.

Roberts says "people of all generations" have always related to Diana's ability to use clothes to make a statement. "She was never one version of herself. She inhabited all of these versions, through clothes."

Dressing The Crown

Fashion tells "a million stories" about one's inner life, says Roberts, "and Diana knew that."

The designer was intent on representing the late royal's emotional arc through her biggest fashion moments — illustrated best in three memorable looks: Diana's wedding dress from Season 4, the revenge dress from Season 5 and the blue swimsuit she wore during a vacation with Fayed, from Season 6.

"The wedding dress is enormous and puffy; there's a sense of wrapping her up in cotton wool. It hides her shape, it hides her personality," she explains. "Then you have the revenge dress, which is the first time we've put any kind of royal member in black when it's not for mourning or for a funeral."

The choice to wear the dress, she continues, "was symbolic, in a way, of marking the end of a marriage, the death of a marriage, the depth of her relationship with the palace — and a kind of rebirth as well."

As for the blue swimsuit, Roberts says it represents a sense of Diana "shedding her skin" as she "becomes stronger" as a person, a mom and a public figure.

"You can see a butterfly coming out," she explains of the evolution, which she describes as running parallel to the royal's journey toward individual ownership and "freedom."

It was important to show how Diana went from being "innocent" and "sheltered" to "getting comfortable in her own skin," says Roberts. In her later years, the princess, who for years had been hidden behind palace walls, intended to show the world her true self through fashion. Roberts strove to convey that same message through costume.

It was through her style that Roberts says she got to know Diana, and eventually she honed what she calls a "Diana algorithm," an intuitive sense of what the princess would have worn despite not having any public images that supported it.

"There is something kind of punk about Diana," she says. "She was everything. She's strong and sexy in a floral dress, she's a working woman when she goes to Bosnia and then she has a 'mom uniform' when she's with the boys."

Roberts stresses that she's a costume designer, not a fashion designer. When it came to criticism about what Diana would or wouldn't have worn in the series, she had to nip that in the bud early on. "I think that would have paralyzed me," she says.

That's not to say she didn't have limitations. As for any project that deals with real-life public figures, Roberts says the Crown legal department was steadfast in making sure they didn't run into "implications with copyright" from designers, given that Diana's outfits were fashion-forward, and designer to boot. Slight alterations had to happen to be sure they weren't exact replicas.

"We had to do multiple iterations of the revenge dress," she explains. "There were moments like that, which can be disappointing for us and disheartening, because of course we'd like to do it exactly as it was. But we have these limitations on us that I think people don't realize."

The 'power struggle' of clothing

When it came to scenes where Diana, the queen and other women were in the same room, Roberts says, it became about designing around a subtextual "power struggle," which ended up serving the actors in the long run.

"We think about the mood of that scene," she explains. "Where's her head at? What is she feeling? Is she feeling powerful? It's often a power struggle that we try to tell through clothes ... who's feeling weaker? Who's the more vulnerable one? Who's the stronger one?"

That doesn't just happen by reading the script, but also through a visual research, which she and her mother are very thorough in doing. "It's an extensive period," she says, much of which is represented through photos that are tacked on a vision board. "It's entirely covered in photographs, quite specifically, of what goes on in the script."

Now, as Netflix gears up to drop the second part of Season 6, which will feature Prince William and Kate Middleton's early romance, on Thursday, all eyes are on Middleton's sheer dress and black underwear, which was previewed in a clip ahead of the release.

It was the dress that the Duchess of Cambridge wore while walking the catwalk at a fashion charity event in 2002, a year after she and William met at the University of St. Andrews.

As for designing Middleton, Roberts is giving her character the same amount of care as Princess Diana.

"With all our work, the idea is to tell the truth, and that's what we plan to do," she says.

Click here for never-released-before photos from the set of The Crown.

The Crown Season 6, Part 1 is streaming on Netflix, with Part 2 premiering on Dec. 14.