Princess Diana's "revenge dress" is being auctioned by Sotheby's

On the same evening that Britain's King Charles, then Crown Prince, admitted in a documentary to his infidelity, his wife, Princess Diana, attended a charity dinner organized by Vanity Fair magazine at the Serpentine Gallery in London.

The plan was to wear an elegant Valentino evening dress. But half an hour before departure, she changed her mind and stepped into a short-short silk dress with bare shoulders and a deep neckline. On her feet were black pumps and around her neck a choker necklace with pearls and sapphires.

For those who are not allowed to verbally express their own opinions or feelings – i.e. royalty – clothes can be both a language and a vent. The deceived, but popularly loved princess responded to her husband's betrayal by breaking Buckingham Palace protocol and allowing herself to be photographed in an all-black creation that exposed her slender, feminine figure.

The following day the British press had coined the term "revenge dress".

Now the garment, which was created by Greek designer Christina Stambolian, is for sale. The auction house Sotheby's will first take it on a tour from London, via Geneva and Hong Kong, before the dress is clubbed in New York in December. It is expected that it will go for between 1.5 and 3 million Swedish kronor.

Of course, it is not the material itself or the craftsmanship that drives up the price, but the story behind it.

The only question is how it should be interpreted.

Angela McRobbie, professor of communication at Goldsmiths College in London, believes that the spontaneous choice of dress carries a "deeply conservative idea". In the prefeminist world, "the young woman who has been deceived could think of no better way to punish her unfaithful lover than through extravagant displays of fashion and the body," as she put it.

Others see the suit as an expression of agency and authority. There is also a third interpretation possibility. Perhaps the iconic black case is simply a mourning dress.

Sotheby's upcoming auction tour confirms one thing: the clothes of royalty are rarely just clothes.