A necklace believed to contain jewels from the infamous Marie Antoinette "Affair of the Diamond Necklace" has been sold for £3.7m.

Set with nearly 500 diamonds and weighing about 300 carats, it smashed price expectations at a Sotheby's auction in Geneva.

The Marchioness of Anglesey wore it at Queen Elizabeth II's coronation in 1953, and it was also worn 16 years earlier at King George VI's crowning.

However, the link to Marie Antoinette, the last queen of France, may have been the most intriguing selling point for the mystery buyer.

Some of the jewels are believed to have been at the centre of the Affair of the Diamond Necklace - a scandal which is said to have paved the way for Antoinette's eventual downfall.

The scandal erupted when a hard-up noblewoman, Jeanne de la Motte, pretended to be the queen and acquired a hugely expensive necklace in her name without paying.

Antoinette, who was accused of having a hand in the scam, was acquitted in a trial. But the affair discredited her further in the eyes of the French people - among whom she was already deeply unpopular.

Her reputation never recovered, her public appearances all but ceased, and the number of pamphlets containing malicious gossip about her increased.

It also added to her reputation for extravagance that helped fuel the French Revolution - with the queen beheaded in 1793.

Jewels from the original necklace - which contained nearly 650 diamonds and weighed almost 2,800 carats - were
later sold on the black market, making them hard to trace.

However, a Bond Street jeweller testified at the time that he bought about 350 of them for just over £10,000, according to Sotheby's.

Experts say the quality and age of the diamonds in the necklace sold on Wednesday point to a match.

"It's likely or possible that some of these diamonds may have come from the famous diamond necklace that led to the downfall of Marie Antoinette," said Jessica Wyndham, Sotheby's head of magnificent jewels.

The Georgian-era piece measures 67cm and hadn't been seen in public for 50 years before it came up for sale.

Its final sale price of over 4.2 million Swiss francs was double its pre-auction valuation.