An Antiques Roadshow expert warned a guest ‘brace yourself’ as he revealed the eye-watering value of a diamond she didn’t think was real.

In an episode that first aired back in 1998 and was recently repeated on BBC One, a woman brought along a brooch for Geoffrey Munn to value in Hull.

The accessory was a family heirloom that originally belonged to the guest’s great-grandmother. 

When Geoffrey was presented with the item, he said: ‘Wow. Say what a marvelous brooch, my goodness me. Is it a family one?’

The woman responded: ‘Yes, it came from my great-grandmother, to my nana, to my mum and then it’s been pᴀssed down.’

Though the exact age was not known, Geoffrey confirmed it was from the 20th Century and had a ‘very art deco design’.

In an episode that first aired back in 1998, a woman brought along a brooch for Geoffrey Munn (right) to value in Hull 

The accessory was a family heirloom that originally belonged to the guest’s great-grandmother

‘What’s even more special about it is that the diamonds used in its manufacture are modern cut,’ he added.

The expert went on to describe the ‘baguette diamonds’ and how the design originated from Mexico.

He added: ‘And here in the middle, we’ve got a rather substantial brilliant cut diamond.’

The surprised guest asked, ‘So it is a diamond?’ to which Geoffrey confirmed, ‘Oh it is a diamond’.

She then confessed that she ‘didn’t think it was’ originally. 

Despite the brooch having some damage to it, the expert went on to give his valuation and said: ‘And you know the direction to which this all this is leading, to don’t you? 

‘That this is a really, substantially good, valuable object. If there’s a chance at putting a name to a maker, then that would add to it even more. 

‘But you have to brace yourself, strap yourself into the seat because we’ve got a really really good one here and if you went into a West End shop to buy such an object again, I think it’s possible that they would ask you £12,000 for it.’

Visibly shocked with wide eyes, the guest exclaimed: ‘Good God. Dear me. We didn’t think these were diamonds.’

‘Well they are diamonds, they’re all diamonds and you’ve got a very valuable brooch,’ Geoffrey replied. 

Despite the brooch having some damage to it, the expert went on to give his valuation o up to £12,000

Visibly shocked with wide eyes, the guest exclaimed: ‘Good god. Dear me. We didn’t think these were diamonds.’

Elsewhere, an episode of the American PBS show saw another guest left staggered after an item they’ve worn every day for decades was given an eye-watering value.

Expert Peter Planes was presented with a Rolex X Tiffany watch to evaluate.

The accessory was gifted to the guest by his late uncle back in 1975, who had bought it from Tiffany’s in New York.

It had been worn by the man nearly every day, who admitted he has ‘never taken it off’ and he even had a watch-shaped tan line on his arm.

The guest explained how he had taken it to Rolex to be serviced, but ultimately decided to go with a different repair shop as the luxury brand wanted to replace the watch’s face.

Peter revealed that because the guest had kept the original features, the value was actually higher and determined the eye-watering sum to be $50,000 (£39,500).

Antiques Roadshow airs Sundays on BBC One and is available to stream on iPlayer.