According to jewellery expert Claudia Joseph, this was “a symbol of glamour from the young Princess.”

However, she seems to have returned it to the Queen in the early 1960s, by when she had acquired her own Poltimore Tiara.

Jewellery was one of the areas where Princess Margaret’s attitude was most modern.

Even on her wedding day, she broke protocol by refusing a family heirloom for the Poltimore tiara, a piece she had bought at auction for less than £6,000 before her engagement.

She wore it on numerous occasions before and after her marriage.