A diamond ring bought at a car boot sale for £10 has been sold for £656,750 at auction in London.
The jewel was expected to fetch £350,000, but went for almost double that at Sotheby's on Wednesday.
The owner believed the "exceptionally-sized" stone was a piece of costume jewellery when she bought it at West Middlesex Hospital in Isleworth, west London, in the 1980s.
Unaware it was a 26 carat diamond, she wore it daily for decades.
The cushion-shaped white diamond is thought to have been from the 19th Century.
Ahead of the sale, the head of the auction house's London jewellery department, Jessica Wyndham, said: "The owner would wear it out shopping, wear it day-to-day. It's a good looking ring.
"No-one had any idea it had any intrinsic value at all. They enjoyed it all this time."
Ms Wyndham said the owner - who does not want to be identified - assumed it was not a genuine gemstone because it was in a "filthy" mount and it did not have the sparkle of a diamond.
It wasn't until after 30 years of wearing the ring that the owners took it to Sotheby's and a jeweller told them it may be valuable.
More tales of boot sale bounty
After paying £10 for a floral vase at a car boot sale, the Hampshire-based owner decided to sell it on eBay.
When bids soared to £10,000, he withdrew it - and sought professional help in identifying just what he'd bought.
The £10 pot was, in fact, a rare enamel "two quails" vase, thought to have been made at Beijing's Imperial Palace at least 220 years ago.
John Axford, Asian art expert at Woolley & Wallis auctioneers, confirmed the "excellent investment" bore the four-character mark of Qianlong - the sixth emperor of the Qing dynasty - and would have been made in the palace workshop between 1736 and 1795.
The firm sold the vase in Salisbury in November 2016, where it made £61,000, including buyer's premium. That was double its guide price of £30,000.
Another eye-catching item from the Sotheby's sale was a Cartier diamond brooch worn by Margaret Thatcher.
It was worn the day she offered her resignation as Prime Minister to the Queen.
With its geometric chevron design, the brooch was eventually sold for £81,250, having been estimated to fetch up to £35,000.
Proceeds from that sale will be donated to charity.
Ms Wyndham said: "It was a thrill to bring the hammer down on two objects which have been the subject of so much interest and attention over the last few weeks and to see that attention translate into such strong bidding competition."