The set features similar diamond and ruby detailing to the Burmese Tiara, which has been worn by the Queen many times.
Alexandra said: “The Burmese Tiara is a fairly modern addition to the Crown Jewels, in comparison to the extensive royal collection.
“In keeping with monarchical tradition, the Queen, Elizabeth II, made use of an existing piece and ordered a new Tiara with Garrard in 1973.
“She re-purposed a wedding gift from the 7th Nizam of Hyderabad, who had in fact gifted her a shopping trip in Cartier.
“The gift in question was a flourished diamond Tiara and Necklace from the 1930s, but only diamonds from part of tiara were used to make her new Ruby diadem.