This sexy little number became iconic when Diana wore it in 1994. Photo / Getty Images

Diana was never meant to wear the dress. Heck, she hadn't planned on going out that night, according to reports. It was June 29, 1994 and that evening, a documentary in which Prince Charles would admit to having been unfaithful to his wife, the Princess of Wales, was set to air.

The Princess could have stayed home, curled up on the couch with her devoted butler, Paul Burrell. She could have had dinner with her trusted cadre of female friends at society haunt San Lorenzos, news.com.au reports.

Instead, Diana staged the most sublime coup-de-force, publically wounding her husband and the sagging edifice of the royal family and in doing so, created one of the most iconic fashion moments of the 20th century. Because that was the night she trotted out the Revenge Dress in a cunning sartorial move that would have surely impressed Anna Wintour, Napoleon and Machiavelli simultaneously.

With millions of Britains set to watch the future King admit to journalist Jonathan Dimbelby that he had cheated on his wife, Diana had, only at the last minute, decided to attend the Serpentine Gallery's summer party, according to the (UK) Telegraph, which is a red letter day on the London social calendar.

Christina Stambolian was a renowned couturier and designer in Lonon. "I am proud to say that for sometime Diana had shown an interest in my work, and had added a couple of my designs to her wardrobe from a boutique in London," she tells news.com.au.

"However, I had not met her, until one [day] unannounced she and her brother Earl Spencer paid me a visit. She wanted a special cocktail short dress. She was such a beautiful woman therefore she should wear something that would do her beauty justice..Something sexy. We then decided that the best colour would be black and the material should be nothing else but silk. Her brother agreed with her and we were all happy," she tells news.com.au exclusively. "Several weeks and a couple of fittings later the outcome of her visit was delivered to her. It was a dress cut to reveal her body quite unlike any style she had worn before."

It was 1992 and the dress would languish in Diana's cupboard for years. Christina thought she might not have worn it "because it was a little too daring for a royal."

However, June 29, 1994 was a night for making a statement.

Diana's former stylist Anna Harvey told a 2013 documentary that of that evening, "she wanted to look a million dollars. And she did."

As her estranged husband tried, in vain, to wrest back some public sympathy with his disastrous interview, Diana adroitly stole his thunder and deftly reclaimed the narrative, her Stambolian cocktail dress landing a killer blow in the War of the Wales'.

Initially, she had been planning on wearing a high-profile designer but when the fashion house jumped the gun and put out a press release touting her choice, peeved, Diana is said to have changed her mind. Instead, she rifled through her walk-in wardrobe in her apartment in Kensington Palace where any number of couture and designer gowns were nestled. And there, she grabbed the sexy dress Cristina had created for her.

Watching footage from her arrival that night Diana strides out of the car, beaming. She is supremely confident and can be seen joking and chatting happily to the waiting gallery staff. She knew what she was doing - she knew which image (apologetic balding man vs dynamic modern woman) would captivate the public imagination.

Says Christina: "I was thrilled…at last it has taken two long years [for her to wear the dress] but it [had]happened."

It was a stunning departure for Diana. After years of trotting out appropriately regal ball gowns and knee-length suits, the Stambolin dress in one fell swoop said goodbye to the strictures and formalities of appropriate regal dressing. Gone were the prim collars and vast swathes of Laura Ashley.

Diana's message was clear: Here was a woman unapologetically embracing her power and her sexuality, for all the world to see. And it was a truly stunning declaration of independence from a woman whose adult life had largely been spent confined by the expectations and rigid habit of an often unsympathetic family.

There is another daring aspect to her look that night which is also worth pointing out. Diana had arrived at the gallery boasting a dramatic, blood-red manicure, a huge no-no for members of the royal family. For Windsor women, nudes or pale pinks are the only colours deemed acceptable by the Queen (she herself has been wearing the Essie shade Ballet Slippers for decades.) Again, she was sending a signal - the old rules no longer applied, we were in thrilling uncharted territory.

The genius of her choice of outfit that night was that by unveiling this ensemble that evening she stole Charles' limelight, relegating coverage of his documentary (which had been 18-months in the making) off some front pages. The next day, The Sun ran a shot of Di with the headline "The Thrilla He Left to Woo Camilla."

Any sympathy that Charles might have hoped to garner with the TV special was drastically eroded as the public struggled to understand why he would prefer a horsey, mother-of-two from Gloucestershire to his bombshell wife. While she was the glamorous modern woman embodying the 90s' dynamism, Charles, and by extension the royal family, looked antiquated and out-of-touch with the zeitgeist. With nothing more than chiffon and some nail polish, she had struck a devastating blow at the monarchy's already hoary image.

Looking back, it is now blatantly apparent that on that June evening, Diana cunningly weaponised fashion, the repercussions of which we are still feeling two and a half decades later. Revenge looks (and revenge bodies) are part of the cultural fabric and the inherent capacity of style to artfully communicate messages about power, identity and agency is something high profile women such as Michelle Obama, Duchess of Sussex and Amal Clooney now deftly deploy.

But that night back in 1994, when Diana stepped out of her chauffeur-driven Jaguar, I wonder if she knew quite how seismic, and significant, her choice of dress would be. Like many women throughout history, it is only in hindsight that their true tactical brilliance is recognised. 25 years on, the Revenge Dress is a truly potent a symbol of female power. Vive Le Revenge Dress.

Daniela Elser is a royal expert and freelance writer with 20 years' experience who has written for some of Australia's best print and digital media brands.