The experts said: “The dazzling diamond and pearl tiara was originally designed for Queen Mary back in 1913 which passed on for her granddaughter. 

“Queen Elizabeth II reportedly presented it to Diana for her royal wedding day in 1981, although she respectfully declined and opted to wear her father’s Spencer’s Family Tiara instead.

“Despite this, the Lover’s Knot became one of her [Diana’s] favourite pieces, although it’s claimed to have been so heavy that it hurt her head.

“The fact that it’s so heavy it hurt Princess Diana’s head indicates that this is a valuable tiara, embellished with the finest quality diamonds and pearls.”