Knight of the Crown
An Order of Knighthood
A player may become eligible for Knight of the Crown after serving with excellence, and completing, four terms in any of the following offices, in any combination, at the Duchy level or higher: Monarch, Regent, Prime Minister, or Champion. The position of Kingdom Monarch counts as two offices. The position of Champion can only be counted once toward these qualifications.
Historical Qualifications
A knighthood in the Order of the Crown is awarded for outstanding leadership. In increasingly few Kingdoms, this Knighthood is awarded to every Kingdom level Monarch upon their stepping down, which has the unfortunate side effect of devaluing the respect some people give Crown Knights. Many Kingdoms now require multiple terms of service in high offices, as well as requiring candidates for Knight of the Crown to display excellent leadership skills.
Check here for as complete a list as we can make of all Crown Knights everywhere.