There are dresses remembered because they are beautiful, and there are dresses remembered because they were an answer. Diana's black silk dress of 29 June 1994 belongs to the second group, and on 9 December this year it goes to auction in New York, at Sotheby's.

The estimate is between 150,000 and 300,000 dollars, or roughly 110,000 to 221,000 euros. Auction houses rarely hit their own estimates where Diana is concerned, and here they expect the final price to cross a million euros. Before the sale the dress will travel to exhibitions in London, Hong Kong and Geneva.

The designer is Christina Stambolian. The dress sat in the wardrobe for three years, never worn in public - stylist Anna Harvey says Diana considered it too daring to wear. Then came the evening when Charles publicly admitted his relationship with Camilla Parker Bowles in a television interview.

That is the key to the whole story. The same evening, in the same country, in the same news bulletin - he gave a statement, and she went out. Nobody had to explain anything. Ever since, the dress has been called "the revenge dress", and she is not the one who named it.

The outfit also included jewellery: a pearl and sapphire necklace made from a brooch given to her by the Queen Mother, pearl and diamond earrings from Collingwood, and a sapphire bracelet said to have been a gift from the Emir of Qatar.

What Diana's clothes are worth today. In 2023 a velvet dress by Victor Edelstein from her wardrobe sold for 604,800 dollars - five times the estimate. Her famous sheep jumper reached 1.1 million dollars, fourteen times the opening estimate. So the market has already shown twice over that estimates for Diana are conservative.

Part of the proceeds goes to the charities NHS Lothian Charity and the Royal Edinburgh Hospital. That is where the story closes cleanly - a piece created as a private answer to a public humiliation is, thirty-two years later, paying for somebody's hospital room.