King of Arms

King of Arms is the senior rank of an officer of arms. In many heraldic traditions, only a king of arms has the authority to grant armorial bearings and sometimes certify genealogies and noble titles. In other traditions, the power has been delegated to other officers of similar rank.
Heraldic duties.
In England, the authority to grant a coat of arms is subject to the formal approval of the Earl Marshal in the form of a warrant. In jurisdictions such as the Republic of Ireland the authority to grant armorial bearings has been delegated to a chief herald that serves the same purpose as the traditional king of arms. Canada also has a chief herald, though this officer grants arms on the authority of the Governor General as the Queen's representative through the Herald Chancellor's direct remit. Scotland's only king of arms, the Lord Lyon, exercises the royal prerogative by direct delegation from the Crown and like the Chief Herald of Ireland and the old Ulster King of Arms needs no warrant from any other office bearer.
In the Kingdom of Spain, the power to certify coats of arms has been given to the "Cronistas de Armas" (Chroniclers of Arms).
The English and Scottish kings of arms are the only officers of arms to have a distinctive crown 
of office, used for ceremonial purposes such as at coronations (as opposed to peers, who instead wear a coronet). At the coronation of Queen Elizabeth II, the kings of arms used a crown trimmed with sixteen acanthus leaves alternating in height, and inscribed with the words "Miserere mei Deus secundum magnam misericordiam tuam" (Have mercy upon me, O God, according to Thy great mercy; Psalm 51). When this crown is shown in pictorial representations, nine leaves and the first three words are shown. Recently, a new crown has been made for the Lord Lyon, modelled on the Scottish Royal crown among the Honours of Scotland. This crown has removable arches (like one of the late Queen Mother's crowns) which will be removed at coronations to avoid any hint of lèse majesté.
Kings of Arms and Heraldic Authorities of the United Kingdom.
Orders of chivalry.
Garter King of Arms is the herald of the Order of the Garter as is in Scotland Lord Lyon King of Arms the herald of the Order of the Thistle. The Norroy and Ulster King of Arms is the herald of the (now dormant) Order of St Patrick. Other British orders of chivalry have their own kings of arms: