A guest of BBC's Antiques Roadshow was left gobsmacked after a family ring, long thought to be a cheap piece of costume jewellery, turned out to be a rare and valuable emerald piece worth more than expected.

The jaw-dropping revelation occurred during an episode first broadcast in October 2022, which was repeated on Sunday.

Filmed at the historic Wollaton Hall in Nottingham, the episode showcased a variety of intriguing items, including a Batman mask donned by Jack Nicholson, poetry, and personal belongings brought to the UK by Ugandan Asians escaping their homeland in 1972.

However, it was a jewellery evaluation by expert John Benjamin that left one family utterly shocked. The guests, two cousins, presented a collection of inherited treasures passed down through generations.

Among the assortment was a gold novelty pencil, a decorative brooch depicting a fly on a flower, and the green stone ring under scrutiny.

Discussing the origins of the items, the guests revealed that many were from their great-great-great grandmother, who was born in 1858. One item, a mountaineer's ice pick-shaped pencil, bore the names of French mountains.

"One assumes that the person who owned this originally was a mountaineer who went on this pioneering expedition," said Benjamin. "And he climbed all these mountains and thought, right, when I get back to London, I'm going to commission a company - Hunt and Roskell - to make a gold novelty pencil fashioned as an ice pick."

He dated this unique piece back to 1879 and estimated its worth between £1,500 and £2,000.The second item, a Victorian brooch depicting a fly resting on a flower, also got Benjamin's interest.

"You can see it's a fly and a flower that looks to me a little bit like, I don't know, it could be a crocus," he observed. The brooch, adorned with malachite, jaspers, and lapis lazuli, was deemed "really unusual".

He dated the piece to around 1845 and valued it between £1,200 and £1,500. However, the biggest revelation came with the final item - a green stone ring that the family had always assumed was costume jewellery.

This heirloom, passed down from their great-great aunt, was given to the guest's mother as a birthday gift. When asked if they thought the ring was costume jewellery, one guest responded: "Um, I think so. Yeah. It doesn't have a lot of weight in it."

Benjamin surprised them with his evaluation: "It's an emerald! It is a splendid Colombian emerald. From South America, surrounded by old Victorian white brilliant-cut diamonds, mounted up in 18 karat gold, made in around about 1875 to 1880."

He valued the ring at a whopping £4,000. In total, the collection was given an estimated auction value of £7,000.

The guest's jaw dropped as the valuation was revealed, with the item estimated to fetch between £5,000 and £10,000. Overcome with excitement, the guest blurted out: "Oh my God. Thank you. Thank you. I'm going to tell Granny now. She'll be eating her words."

Antiques Roadshow is available to watch on BBC One and BBC iPlayer.