A crown denotes sovereignty and is worn by the sovereign of the country. The crown and other regalia are used in the consecration ceremony of the crowning of the Sovereign; the last to take place in the UK was that of HM The Queen at her coronation in June 1953.
The crown jewels of the British monarchy have been used since 1660 or even earlier and they have an interesting history. In 1841 fire broke out at the Tower of London and they were removed from their display by bending the bars as the key could not be found and in 1671 an attempted robbery took place by Colonel Thomas Blood. The crown jewels have been housed at the Tower of London since 1303 and in 1994 the Queen opened a new display room which uses new technology to aid public viewing of the jewels.
Burke's Peerage's Guide to Royalty