Kate Middleton wedding: Duchess wore £1million Cartier halo tiara to marry Prince William

Eddie continued: “The Lover’s Knot Tiara has 19 diamond arches with 19 hanging pearls, all set in silver and gold.

“I estimate from having seen photographs of this tiara that it is made up of 85 carats of diamonds, the largest of which are three carats each, while the 19 pearls appear to be natural.

“I would value this tiara at approximately $3million [£2.4million] and at auction, well in excess of $25million [around £20million].”

Lotus Flower Tiara

The pricey jewel has been worn by members of the Royal Family including Queen Elizabeth the Queen Mother and Princess Margaret.

If the tiara was to be sold at auction, the jewellery specialist explained it could pick up as much as £16million.