The auctioneer described the bidding in the sale room as “really fierce” with private buyers vying with institutions and collectors, but it was bought by an unnamed overseas museum for £156,000, including buyer’s premium.
At the time of the banquet Diana reportedly whispered to the Emir of Bahrain: “What would be your reaction if your son was to marry a tall, blonde English woman.”
And he reportedly replied: “I would be very jealous.”
The seller only realised she had bought something special when saw the dress while watching a recent documentary about the princess, and re-discovered it carefully folded in a box in the bottom of her wardrobe.
The dress originally cost £200 and was bought in £50 instalments, it had an estimated sale price of £60,000-£100,000.
At the time the seller also bought a jacket worn by Diana, a Chelsea Design Co smart navy wool blazer the princess slipped on when away from royal duties.
It sold for £2,280, including buyer’s premium, at the Kerry Taylor Auctions sale.
Both items had been taken to the secondhand shop by a housekeeper working for one of Diana’s close friends.
The auctioneer added: “The housekeeper that took the dress in to the shop took in lots of things like dresses by Bruce Oldfield.
“I think in Hereford people have in their wardrobes other Princess Diana dresses and they don’t know about it.”