Princess Kate's diamond and sapphire engagement ring has a hidden meaning few know about

Prince William's proposal to his then-girlfriend Kate Middleton was as romantic as it gets, with the royal popping the question to his university sweetheart during a private holiday to Kenya.

The Prince of Wales famously proposed with his late mother's diamond and sapphire engagement ring, which she had picked out from Garrard ahead of her marriage to King Charles in 1981.

12 years on, the Prince and Princess of Wales are still happily married, and Princess Kate's heirloom ring remains one of the most recognisable royal engagement rings in the world - but did you know it bears a strange, secret symbolism?

Princess Kate's sentimental sparkler would have cost approximately £28,500 at the time of Princess Diana's proposal, which would make it worth £102,501 in line with the Bank of England's inflation calculator today. However, other reports have suggested the value could now be up to £390,000.

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It's not the cost that is symbolic, though. According to Justin Daughters of Berganza, the prestige of sapphires holds a seriously impressive history.

"Some of the most notable stones were found in Ceylon, Burma and Kashmir back in the 14th Centure," says Justin. "Kashmir sapphires, famed for the superiority of their colour and velvety appearance, continue to be a truly sought after rarity."

Justin added: "Sapphires were once believed to protect wearers from the effects of poison - including snake bites - they’re now more commonly associated with sincerity, truth and faithfulness." 

While it seems unlikely that Prince William had snake bites on the mind when he was proposing to his wife-to-be back in 2010, there is an undeniably romantic connection between the rare stone and it's believed associated with faithfulness and loyalty.

In their first interview after announcing the engagement, the Prince explained he'd planned it for a while and carried his mother's sapphire and diamond engagement ring in his rucksack for three weeks before proposing and was terrified of losing it.

Kate called the moment "very romantic," before admitting it was a "total shock," but the couple admitted they'd discussed marriage with each other a lot in the previous year.