Hello all:
This is my first posting, but I am glad to identify the tiara worn by HRH The Duchess of Cornwall in the 2 pix posted by Flower007.
It was made for Queen Mary for the Delhi Durbar in 1911, when she and King George V travelled there to be crowned as the Emperor & Empress of India (the only monarchs to have done so). Originally, Queen Mary used large emerald drops known as the Cambridge Emeralds (also used interchangeably with pearl drops in the Grand Duchess Vladimir tiara owned by HM The Queen and inherited from Queen Mary) to stand upright at various points on this tiara. The tiara was made by Garrard's especially for the Durbar in India, and was referred to by King George V as, "...May's best tiara." In fact, it should be more correctly termed a "diadem", since it fully encircles the head. I've not seen this jewel in any photograph, and am not aware of its having been used by anyone since Queen Mary's death in 1953. Queen Mary left it to the late Queen Elizabeth the Queen Mother, who in turn left it to HM The Queen. It is the personal property of HM The Queen, and is not part of the Crown Jewels. Also, when used originally in India in 1911, the Cullinans III and IV were set centrally.