On 29 July 1981, 750 million people in 74 countries watched Diana Spencer walk into the cathedral in a dress that would become the most copied wedding gown of the twentieth century. Forty-five years later, a fashion historian says the design actually pointed to another queen - the one who ended under the guillotine.

Historian Amber Butchart, on a BBC programme devoted to the history of clothing, draws the line between Diana's gown and the portraits of Marie Antoinette painted by Élisabeth Vigée Le Brun. The enormous gathered sleeves, the ruffled neckline - that is the silhouette of the chemise à la reine, the dress with which the French queen caused a scandal in a Paris salon in 1783.

The numbers on the dress itself are almost absurd: 25 metres of silk and taffeta, 90 metres of tulle and 10,000 pearls and mother-of-pearl sequins. Designers David and Elizabeth Emanuel described it as „appropriately dramatic”. For an event watched by three quarters of a billion people, drama wasn't a stylistic choice but a technical requirement.

This is where the word the media use for this story comes in - premonition. Marie Antoinette was executed in October 1793. Diana died in a car crash in August 1997. Both women entered the institution from outside, both were shaped into a symbol, and both ended up as the subject of people who never knew them.

But calling that a premonition is a lovely sentence that doesn't hold water. Nobody in 1981 was designing an ending; they were designing splendour. What actually repeats is not fate but a pattern: an institution takes a young woman, turns her into the image it needs, and then doesn't know what to do when the image starts living on its own.

That is exactly what makes the dress interesting even now. Not as a fairy-tale relic, but as the first document of the production - the moment one person became material to be processed for decades. Thirty metres of fabric, ten thousand pearls, and seven hundred and fifty million pairs of eyes watching.

The wedding was the beginning. The question rarely asked is whether anyone ever asked her what she wanted to wear.