This badge of office was given to Dione when she became the Countess of Verulam DL as Her Majesty's Lord-Lieutenant for Hertfordshire in June 2007.
The Lord Lieutenant is appointed by The Queen, on the advice of the Prime Minister and is Her Majesty's personal representative in Hertfordshire.
There is no prescribed uniform for a Lady Lord-Lieutenant, but there is this badge which can be worn on ceremonial occasions.
A male Lord-Lieutenant wears an uniform which follows the style of an Army No. 1 dress. It is made from dark blue barathea material, with trousers having a scarlet stripe. In England Lord-Lieutenants have a cap badge and buttons bearing a Crown above a Tudor Rose. The ceremonial uniform includes a sword with a steel scabbard.