Hereditary succession is the element common to all monarchies, save for rare historic examples of election such as in Poland and the Holy Roman Empire, and in the modern example of the Papacy.
As an aside: It is also interesting to note the Anglo-Saxon tradition of the “election” of a new king by the Witenagemot from amongst the deceased King’s family. Although tempting to draw a comparison with Parliament’s invitation to William and Mary in the seventeenth century and the installation of George I in the eighteenth, the power of the Witenagemot was never so great and, in practice, amounted to little more than formal recognition of the king’s established (primarily primogenital) heir. Nevertheless, I regard this Anglo-Saxon recognition as an early form of the concept of covenant/consent which was to be settled in England after 1689. As evidence I can cite two occasions where it is believed that the Witan deposed a king (Sigeberht, King of Wessex in 757 and Alchred, King of Northumberland in 774) and one where the Witan offered to restore a king on the condition that he improve the quality of his kingship (Elthelred the Unready had fled the country in 1013).
Various different forms of hereditary succession have been employed in different countries:
1. Absolute or lineal promogeniture, also known as full cognatic priomogeniture: inheritance by the oldest child, irrespective of gender. The first monarchy to introduce this was Sweden in 1980 (displacing Prince Carl Philip as Heir Apparent in favour of Crown Princess Victoria).
2. Agnatic or patrilineal primogeniture: inheritance by the eldest son, and then his male issue inheriting before brothers and their male issue. (this is also Salic law)
3. Agnatic-cognatic primogeniture allows female agnates (or their descendants) to inherit once there are no surviving male agnates.
4. Male preference primogeniture (also known as "mixed-female succession" and as "cognatic" primogeniture) allows a female to succeed if she has no living brothers and no deceased brothers who left surviving legitimate descendants.
5. Matrilineal primogeniture is a form of succession where the eldest female child inherits the throne to the total exclusion of males.
6.Uterine or ovarian primogeniture a right of succession may also be inherited by a male through a female ancestor or spouse, to the exclusion of any female heir who might be older or of nearer proximity of blood;
Succession provides the continuity that is essential to the stability of Monarchy. According to the common law Doctrine of Perpetuity, the Sovereign never dies but is immediately succeeded by his or her successor. Hence the expression: “The King is Dead! Long Live the King!” The individual Monarch may die but the Crown continues, for it is the source of all authority and without it the state would cease to be.
The continuity afforded by Monarchy through hereditary succession enables the public to understand and tangibly connect with the stability of the political system. The Monarchy provides the nation with all-important reassurance in a world which is changing ever more rapidly. The Monarchy grounds us; it promotes order, symbolises essential values and provides us with a sense of national identity and unity.