The diamond jewel was borrowed from the Queen and could be worth more than £1million, according to gemologist and jewellery expert Deborah Papas.
She said: “It is very hard to estimate the value but as a Cartier piece, I would estimate it to be worth approximately £750,000 to £1.25million.”
Lover’s Knot tiara
Before Kate wore the headpiece, it had been worn by royals including Princess Diana.
The large tiara is covered with diamonds and pearls and could reportedly fetch as much as £18million.
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It is thought to be made up of 85 carats of diamonds with 19 natural pearls.
The Lotus Flower tiara
Previously a favourite of Princess Margaret, Kate has worn the Art Deco piece on two occasions.
Speaking about the tiara Alexandra Michell, Gemologist Prestige Pawnbrokers Hatton Garden, said: “The Lotus Flower tiara was commissioned by the Queen Mother in 1923, converting a gift from her husband George VI. The gift in question was a diamond necklace from Garrard, which had a completely different Grecian design.
“A historical and stylish piece such as this, would no doubt achieve in the regions of £4million.”
Teardrop earrings
At the end of 2019, Kate borrowed a pair of glitzy teardrop earrings that were first worn by Queen Elizabeth II in 2012.
While their value is not known, they are sure to be worth a small fortune due to their rarity and royal link.
Irish Guards Brooch
The brooch was worn by Princess Anne when she handed out shamrocks to celebrate St Patrick’s Day each year from 2002 to 2011.
Kate has continued to wear the gold pin since taking over the role from Princess Anne in 2012.
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The royal line of succession – who outranks who?
The line of succession to the British throne dictates the order in which each member of the Royal Family would ascend to the throne.
It is also seen as a ranking of importance with the head of the line, the Queen, taking the place of ruler.
Older children come before younger children. Traditionally boys came before girls, but this law was changed on 26 March 2015 before the birth of Prince William’s first child.
Incredibly, Catholics are still excluded from the line of succession, as are children born outside of wedlock.
The royals, who usually stick to a strict protocol when appearing in public, often arrive at events in ascending order of importance, with the most important royal arriving last.
Prince Charles, 71, is currently second-in-line to the British throne, followed by Prince William, 38, his oldest son.
Then comes Prince William’s children, George, seven, Charlotte, five, and Louis, two, and they are followed by Prince Harry, 35. Prince Harry is succeeded by his son Archie Harrison, born in May 2019.