A £10 car boot ring bought in the 1980’s sold at Sothebys in 2017 for £656,750 because for thirty years nobody could tell it was real. But the interesting part of the story isn’t the extraordinary return. It’s why nobody recognised that it was a stunning diamond in the first place.
In the late 1980s, Debra Goddard went to at a car boot sale in Isleworth, west London, wanting to buy the bangles. The seller wouldn’t split the box, so she haggled the £12 price down to £10 and took the lot home. In amongst the bangles was a cocktail ring – made up of a large clear solitary stone in a dull, tarnished setting. It didn’t sparkle and she assumed it was costume jewellery, which is probably what most of us would assume when faced with a stone that size that simply didn’t behave like a diamond and you’ve bought for £10. She slipped it on her finger and for the next thirty years she wore it, to the shops, on the bus, doing her groceries, and thought nothing more of it.
In 2017, a local jeweller suggested she have it looked at. It went to Sotheby’s and then to the GIA, which certified it as a 26.27-carat antique cushion-shaped diamond of the nineteenth century, VVS2 clarity and I colour. Nicknamed the Tenner, it led to a Sotheby’s Fine Jewels sale in London on 7 June that year with an estimate of £250,000 to £350,000 but sold for an incredible £656,750, almost double the top estimate. Jessica Wyndham, then head of Sotheby’s London jewellery department at the time said, “The first time I saw the diamond in person it was clear that it was a special stone.” and told the BBC later that the owner “had enjoyed wearing the ring for years without anyone having the faintest idea it had any intrinsic value at all”.
Sotheby’s has just put this story back in front of its audience, nine years later. I can see why – it’s a dream scenario. Most people visit or watch the Antique Roadshow to know the price of the thing thats been left in the attic for fifty years. This is the same story but impossibly multiplied. Someone bought something for a tenner and discovered it’s worth more than half a million pounds. But there is something else going on here, and in 2026 it feels considerably more relevant than it did in 2017.
For more read : Why everyone is suddenly talking about brown diamonds
Why didn’t it sparkle?
The Tenner looked wrong because it was cut for a completely different world. A nineteenth-century cutter worked with the natural shape of the stone and tried to preserve as much of the rough of the diamond as he could. The stone itself was what was being preserved. Old cuts have larger facets, high crowns and open cutletss, and they weren’t designed to glimmer in harsh modern lighting but instead under candlelight. “They don’t necessarily have the sharp, restless brilliance that we have come to associate with diamonds. They have a softer glow,” Wyndham says. “Unlike modern diamonds, which are cut to maximise brilliance and return of light, older diamonds were fashioned to display their “fire,” which is the splitting of the light into its spectral colours. It would have looked magnificent in the candlelight of the time.”
Put one under an LED strip however and it can look surprisingly flat. Add more than a century of tarnish to the setting, years of dirt to the stone and then put it in a box of costume jewellery at a car boot sale, and suddenly it isn’t so extraordinary that nobody recognised it. It could have been any piece of costume jewellery.
Modern brilliant cutting changed all of that. Over the twentieth century we became extraordinarily good at cutting diamonds to return light, sacrificing more of the rough to achieve the symmetry, brilliance and fire that we’ve come to expect in a diamond. In the process we also taught generations of consumers what a diamond was supposed to look like. It’s supposed to sparkle. And that is why the Tenner becomes a much more interesting story today.
For more about diamonds read our guide – how to buy diamonds.
This is where it becomes uncomfortable
A diamond can now be grown in a vacuum chamber that looks and does exactly what consumers have spent decades being taught a valuable diamond should do. It can be bright, white, clean and brilliantly cut, and it can be sold for a fraction of what the equivalent natural diamond would once have cost. The visual characteristic we have relied upon most heavily to communicate diamond value has become the easiest part to reproduce. Sparkle is no longer a rarity. It can be made, grown, manufactured. And this is why we’ve seen this year diamonds being the accompaniment to larger coloured stones, to enhance them rather than being the star themselves.
Why the Tenner became invisible is that nobody today can manufacture another nineteenth-century 26.27-carat diamond. Nobody can recreate the geological event that formed it, the world from which it came or the hand that cut it for candlelight more than a century ago. Or even the way it was cut.
Wyndham made another interesting observation when the stone emerged in 2017. A diamond of that size and date would almost certainly have belonged to someone of considerable wealth. Before the great South African discoveries transformed diamond supply in the late nineteenth century, stones of this scale were extraordinarily scarce. Yet we don’t know who owned it. We don’t know how it ended up in Isleworth or how many hands it passed through before somebody put it into a box of jewellery and accepted £10 for the lot. That missing history makes the object more interesting, not less.
But there is a bigger point here. For thirty years people looked at a 26.27-carat nineteenth-century diamond and saw costume jewellery because it didn’t display the characteristic we had taught them to associate most strongly with value. Today we can manufacture that characteristic almost perfectly in a matter of days. What we can’t manufacture is everything they overlooked.
The next Tenner is probably out there somewhere, dull and dirty in somebody’s jewellery box, still hiding in plain sight. And perhaps the lesson isn’t that we should all start rummaging around car boot sales. It’s that somewhere along the way we became very good at recognising sparkle, and rather less good at recognising rarity.
And what of ‘Tenners’ discoverer? Debra Goddard can still to be found rummaging through car boot sales looking for the next ‘Tenner’.
Like this? Read about a Rare brooch owned by Napoleon to be sold by Sotheby’s
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