Diamond ring bought at car boot sale 30 years ago is expected to fetch £350,000

A LARGE diamond ring is expected to fetch £350,000 at auction 30 years after its owner paid £10 for it at a car boot sale, thinking it was a costume jewel.

The “exceptionally-sized” stone was presumed not to be real because 19th-century diamonds were not cut to show off their brilliance like today’s gems.

And so the owner, unaware of its value, wore it for decades, while doing everything from the shopping to the chores.

The 26.27 carat, cushionshaped white diamond, snapped up at a Sunday sale at the West Middlesex Hospital in Isleworth in west London in the 1980s, is due to be sold at Sotheby’s in July.

The auction house’s head of London jewellery department Jessica Wyndham said: “The owner would wear it out shopping, wear it day-to-day. It’s a good-looking ring. But it was bought as a costume jewel. Noone had any idea it had any intrinsic value at all. They enjoyed it all this time.”

Ms Wyndham said that after about 30 years of wearing the ring, the owners took it to Sotheby’s after a jeweller told them it could have substantial value.

“They came in with the idea that it might be real and they had no idea of its value,” she said. “We had a look and said ‘I think that’s a diamond’ and we got it tested at the Gemological Institute of America.”

She added: “The majority of us can’t even begin to dream of owning a diamond that large.”

The diamond ring will be offered as part of Sotheby London’s Fine Jewels sale on July 7.