The Most Ancient and Most Noble Order of the Thistle is second only in precedence to the Order of the Garter and represents the highest honour in Scotland. The Queen is Sovereign Head of the Order.

Her Majesty wears the mantle, hat and insignia of the Order on ceremonial occasions, such as the installation of a Knight of the Order, which take place in the Thistle Chapel at St Giles Cathedral, Edinburgh.
The mantle is of dark green velvet, lined with white and is embroidered with a representation of the Star of the Order.

The hat of black velvet has a plume of white ostrich feathers and an embroidered badge of a thistle surrounded by the motto of the Order NEMO ME IMPUNE LACESSIT (‘No one harms me with impunity’). The collar of the Order consists of a gold and enamel chain comprised of thistles and rue, and the badge suspended from it is an enamelled representation of St Andrew carrying the cross of his martyrdom.