Louisa McDonnell, Countess of Antrim wears a tiara of diamond circles for the coronation of King George V and Queen Mary, 1911; I don’t have any additional information about the tiara

Alexandra “Sacha” Phillips wears a large diamond floral tiara at her wedding to the Marquess of Hamilton (later the 5th Duke of Abercorn) at Westminster Abbey, October 1966; unfortunately, I don’t have additional information about the tiara

Priscilla Annesley, Countess Annesley wears a tall diamond tiara in a portrait published in The Sketch, May 1902; the tiara, appropriately for the time, appears to be an example of belle epoque design