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The Duchess of Cambridge's engagement ring, which once belonged to the late Princess Diana, could be worth about £390,000 now, according to jewellery specialists.
Prince William proposed to then-girlfriend Kate Middleton in Kenya in 2010, with the ring that his mother had worn during her relationship with Prince Charles.
The famous sapphire piece was bought for £28,000 back in 1981 when Charles proposed, but could fetch around £380,000 nowadays, according to specialists at Est1897.
Ben Jarret from Est1897 said: "Royal engagement rings often contain family heirlooms, with diamonds being passed down and often re-set into new bands.
"Kate's is no different, with Princess Diana's engagement ring passed onto her from William. The ring features a 12-carat oval blue sapphire, cut into facets, and surrounded by fourteen solitaire diamonds. The setting is made from 18 karat white gold.
"On their tenth anniversary, we estimate that the ring is now worth £390,000 based on the value of the stone and band, although with the ring being an iconic cultural piece, it could fetch hundreds of thousands more if it ever reached auction."
The ring was made by historic luxury jewellery designer, Garrard, and was originally in Prince Harry's possession after the death of Diana in 1997.
But Harry decided it should be William's when he was ready to propose to Kate.
According to Paul Burrell, Diana's former butler, William had chosen Diana's Cartier watch and Harry had picked the ring.
Burrell told The Diana Story documentary that before William's proposal: "Harry said to him: ‘Wouldn’t it be fitting if she had Mummy’s ring?’
"Then one day that ring will be sat on the throne of England."
Harry had diamonds from his mother's collection used in the ring with which he proposed to his now wife Meghan Markle, in 2017.
The Est1897 experts estimated Meghan's 5-carat ring would be worth about £134,500.
Last summer it was revealed that Harry had extra diamonds added to the band of the ring to mark their first anniversary.
Their biography, Finding Freedom explained: "On May 19, 2019, Harry also surprised his wife of one year with the gift of a ring that he had created with jeweller-to-the-stars Lorraine Schwartz, a favourite of Meghan’s.
“The conflict-free diamond eternity band paid homage to the family of three with Meghan’s, Archie’s and Harry’s birthstones (peridot, emerald and sapphire respectively) on the underside of the ring.”
It adds: “Harry also thought to have Lorraine resize and reset Meghan’s engagement ring with a new diamond band.”
Of course neither ring is likely to be for sale any time soon.
Prince William and Kate are marking their 10th wedding anniversary on 29 April. The couple married in Westminster Abbey in 2011, with 1,900 guests and millions of people watching around the world.
Watch: William and Kate's fairytale wedding