King George IV State Diadem

The Queen’s Diamond Diadem is a beautiful head ornament and probably the most familiar piece of the Queen's jewellery because of its frequent appearance on postage stamps and coins.

The order for the diadem was placed with Rundell Bridge & Rundell (jeweller) in 1820 and the work was complete for King George IV’s extravagant coronation the following year. The design incorporates the national emblems of England (rose), Scotland (thistle) and Ireland (shamrock). There are 1,333 diamonds including a four-carat pale yellow brilliant in the centre of the front cross and 169 pearls. 

In 1838 the diadem was reset with pearls and diamonds from the royal collection and worn for the first time by Queen Victoria at her coronation. For the next thirty years she wore it constantly at her children´s christenings and weddings, at State banquets and she is pictured wearing it on the world´s first postage stamp issued in 1840.

 In her will she left it to the Crown.

The diadem has been regularly worn (and slightly modified) by queens regnant and consort.

 Today it is worn by The Queen when travelling to and from the State Opening of Parliament.

The State Diadem is on display in the special exhibition 'The Queen's Coronation 1953' at the Summer Opening of Buckingham Palace.

References:
Field, Leslie. The Queen´s Jewels. The Personal Collection of Elizabeth II. Harry N. Abrams Inc. 1987