The black taffeta dress worn by Princess Diana at her first official appearance as Prince Charles' fiancee in 1981 was sold for £192,000 (more than R2 million).
The dress, which had been estimated to fetch between £30-£50,000, was designed for the then 19-year-old by former couple Elizabeth and David Emanuel, who later created Diana's wedding dress.
Offered for sale by Kerry Taylor Auctions in London in a "Passion for Fashion" auction, it was bought by a fashion museum in Chile.
Diana and Charles married in July 1981, but separated in 1992 and divorced in 1996. She died in a Paris car crash in 1997.
Charles went on to marry former girlfriend and mistress Camilla Parker-Bowles.