“It was a wedding gift to Princess Elizabeth from the Nizam of Hyderabad, one of the richest people in the world.
“The Nizam is said to have generously instructed Cartier to let the bride-to-be pick anything she wished from their collections, to which the young princess chose a tiara with three detachable flower brooches and what we now know as the Nizam of Hyderabad Necklace Necklace.”
As well as being a firm favourite of the Queen’s, the monarch has also lent this piece to Kate, Duchess of Cambridge for some events in recent years.
Ms Borrowman added: “Featuring more than 50 diamonds set in platinum, the Queen has worn this extravagant necklace in numerous portraits before her coronation and has even lent it to the Duchess of Cambridge on numerous occasions in recent times.