A set of pearls once belonging to Marie Antoinette and taken to Britain by a friend for safekeeping will go on sale in December, and are expected to fetch up to $800,000.
Now part of a diamond, ruby and pearl necklace, France's last queen gave a bag of pearls and diamonds to Lady Sutherland, the British ambassador's wife, before she fled revolutionary France in 1792, a year before Marie Antoinette's death.
"Lady Sutherland was wife of the ambassador and friends with the queen, and they had children of the same age," said Raymond Sancroft-Baker, senior director of Christie's jewelry in London.
"When you are in a dire situation, there are not many people you can trust and the key was to give the jewels to someone with diplomatic immunity," he told Reuters.
According to Christie's, Sutherland arranged for clothes and linen to be sent to the queen while she was in prison.
"This was reportedly the last gesture of kindness shown to the doomed queen," the auctioneer said in a statement.
Marie Antoinette was executed by guillotine in October 1793.
The diamonds were made into a necklace, while the pearls were mounted later for the occasion of the marriage of Sutherland's grandson in 1849.
The pearls, have never been offered at auction before and remained in the same family for over 200 years.
The necklace will go under the hammer at the Magnificent Jewellery sale in London on December 12, and is expected to make between £350,000 and £400,000 pounds ($700-800,000).