Originally, the piece was made as a circular crown of diamond-set papyrus leaves, but Mrs Greville thought it was too large, and had it remodelled in 1910.
In 1919 it was adjusted again so that it could be worn lower on the forehead – a huge trend of the 20s.
Its final tweak was in 1921 when the geometric pattern of diamonds of emeralds was added and this is the version Princess Eugenie wore down the aisle.
Speaking exclusively to express.co.uk about the piece, Alexandra Michell, Gemologist at Prestige Pawnbrokers of Channel 4’s Posh Pawn said: “The tiara originally belonged to Dame Margaret Greville and was left to The Queen Mother (then Queen Elizabeth) in 1942.
“It then subsequently passed to Her Majesty, The Queen and it had not been worn by any member of the Royal Family until Prince Andrew’s daughter showed it off beautifully complimented by her dark wispy hair on her wedding day.