The body politic is a medieval metaphor that likens a nation to a corporation  which had serious historical repercussions throughout recent history and therefore giving the Crown: "As a legal entity today the Crown as executive is regarded as a corporation sole or aggregate",   a corporate entity.    Maitland argues that the Crown (as a legal term) is a convenient cover for ignorance and traces the legal term Crown as corporation sole originally from the 16th century and argues that it was both a political and legal ploy originally reserved for the monarch of the day with the combination of medieval Roman law amalgamated into the early medieval domain of early church property law.   The modern understanding of the concept means a body politic comprises all the people in a particular country considered as a single group. The analogy typically includes reference to the sovereign head of government as head of state,  though the analogy may also be extended to other anatomical parts, as in political readings of Aesop's fable of " The Belly and the Members".
A later European reference to the concept appears in The Book of the Body Politic (1407) by poet and court writer Christine de Pizan, in which she admits having borrowed the concept from a letter of Plutarch's to the Roman Emperor Trajan but does not mention John of Salisbury's work, Policraticus.   The metaphor appears in the French language as the corps-état.  The metaphor was elaborated in the Renaissance, and subsequently, as medical knowledge based on Galen was challenged by thinkers such as William Harvey. Analogies were drawn between supposed causes of disease and disorder and their equivalents in the political field, viewed as plagues or infections that might be remedied with purges and nostrums. 
The term "Body politic" (the political body of society) derives from the mediæval political concept of the King's two bodies first noted by mediaeval historian Ernst Kantorowicz, as a point of theology as much as statehood. However, the person to give the concept some legal bite and codified reality, as much as legitimacy as well as Sovereignty, was the 14th century judge Sir William de Shareshull in 1351 for the offence of high treason   in the aftermath of the Barons war. However, by the time of the fifteenth-century judge Sir John Fortescue the concept moves away from theology to jurisprudence in his The Difference between an Absolute and a Limited Monarchy, written from exile in about 1462 . Fortescue explains that the character angelus (divine character) of the king is his royal power, derived from angels and separate from the frail physical powers of his body. However, he uses the phrase body politic itself only in its modern sense, to describe the realm, or shared rule, of Brutus, mythical first king of England, and how he and his fellow exiles had covenanted to form a body politic. Unusually for the time, Fortescue was writing in English and not Latin: "made a body pollitike callid a reawme." The early medieval period (13th century) saw a general and radical shift in the idea of the political body and sovereignty and who was to be ultimate ruler of humankind.This constant shift in Translatio imperii and The Halo of perpetuity(Kantorowicz reasoning)  transformed the king's persona from Liturgy to legal science, argues Kantorowicz.  However, the Norman conquest proved one thing, quite surprisingly enough, the king wasn't the ultimate and major landowner with just 20% of land ownership as William the Conqueror  found out to his disgust and chagrin, which ultimately led to the Domesday book being compiled. With Plenitudo potestatis, Unam sanctam (a Papal bull) extra Ecclesiam nulla salus and the Sun and moon allegory now part of the armoury of jurisdictional power of the papacy with both Canon law, and medieval political theology now becoming(part of the Scholastic movement beginning with Thomas Aquinas and John of Salisbury) a standard bearer for medieval political power which then descended into the infamous Inquisition and heresy (deviation from truth)as the ultimate legal reality which meant both the Roman Catholic Church and Papal supremacy couldn't be ignored(not without fear of excommunication and in some cases judicial execution). The church, which ultimately had powerful claims to sovereignty due to their immense wealth and vast monetary resources which included a clever taxation system establishing the legal validity of the tithe system which baffled legal experts of the day of its historical lineage and origin, such as Sir William Blackstone, for example, not its legal validity; such as their (the church's) enormous network and ownership of land, law making and the then-University and education system.
In 1550 the jurist Edmund Plowden merged Fortescue's concepts, at the same time removing them from abstraction into a real, physical manifestation in the body of the king. Plowden reports how lawyers codified this notion in an examination of a case of land-ownership turning on a disputed gift by an earlier monarch; they determined that the "Body politic…that cannot be seen or handled…[is] constituted for the direction of the People…[and] these two bodies are incorporated in one person…the Body politic includes the [king's] Body natural."  In 1609 Attorney General Edward Coke pronounced his dissenting opinion, that mortal power was God-made while the immortality of royal power existed only as a man-made concept; Coke later succeeded in limiting the royal power of both Charles I and James VI and I with his now infamous judgements of Case of Proclamations  and his Petition of Right, which triggered off the English Civil War and would have reverberations right across the country for the next 100 years. When the monarchy, in the person of Charles II, was restored at the end of the Commonwealth the idea remained current and royalty continued to use the notion, as a buttress to its authority, until an assertion of the rights of Parliament brought about the Glorious Revolution of 1688.   In the 18th century English Barrister and judge Sir William Blackstone developed further the medieval idea and the legal argument (which still stands today) of the monarch in legal terms "immortal" with added emphasis of a quasi divine (character angelus) status.   
The pre-Revolution monarchs of France also claimed legitimacy on this principle, and extended it to include the idea that the king's heir assimilated the "body politic" of the old king, in a physical "transfer of corporeality", on accession. 
Kenneth Olwig (2002), Landscape, nature, and the body politic, University of Wisconsin Press, p. 87,
The frontispiece to Thomas Hobbes's Leviathan ... is a particularly famous example of the depiction of the body politic ...
- Ulrike Malmendier Law and Finance At The Origin A Historical Case Study:The Roman Corporation 2008
- Edited By Lord Mackay (2014). Halsbury's Laws Of England Volume 29(5th Edition). LexisNexis. pp. 3–4.
- Fredrick, Maitland (1901). "The Crown As Corporation". Law Quarterly Review. 17: 131–146.
They may serve to attract a little interest to that curious freak of English law, the corporation sole. In a previous paper I have written something concerning its history.I endeavored to show that this strange conceit originated in the sixteenth century and within the domain of what we may call "church property law".
- Frederic, Maitland (1901). "The Crown As Corporation". Law Quarterly Review. 17: 131–146.
Oxford English Dictionary,
A nation regarded as a corporate entity
- David, Runciman; Magnus, Ryan (2003). Maitland: State, Trust and Corporation. Cambridge.
- George, Garnett (1996). "The Origins Of The Crown". Proceedings Of The British Academy. 89: 171–214.
- Getzler, Joshua (2016). "Frederick William Maitland Trust and Corporation". University Of Queensland Law Journal. 35 (1): 171–191.
Equity is a difficult subject. ‘Equity’ here denotes the Chancery courts’ system of control of managerial and vulnerable relationships that grew up alongside the common law from the mid-14th century, and which shapes our law still, from contract and family law through to property, commercial and company law. Frederic William Maitland’s late, great, sprawling, and challenging essay ‘Trust and Corporation’ of 1904 sums up his vision of the role and importance of Equity, and is one of the summits of his oeuvre.
- A. D. Harvey (2007), Body politic: political metaphor and political violence, Cambridge Scholars Publishing, ISBN 978-1-84718-272-2
- Christine de Pizan The Book of the Body Politic pp.xviii-xx Kate Langdon Forhan 1994.
- The Book of the Body Politic pp.3-5 1994
- de Baecque, Antoine (1997). The Body Politic: Corporeal Metaphor in Revolutionary France, 1770-1800. Trans. Charlotte Mandell. Stanford, CA: Stanford University Press. p. xv. ISBN 978-0-8047-2817-1.
- Jonathan Harris (1998), Foreign bodies and the body politic: discourses of social pathology in early modern England, Cambridge University Press, ISBN 978-0-521-59405-9
- "Declaration what Offences shall be adjudged Treason. Compassing the Death of the King, Queen, or their eldest Son; violating the Queen, or the King’s eldest Daughter unmarried, or his eldest Son’s Wife; levying War; adhering to the King’s Enemies; killing the Chancellor, Treasurer, or Judges in Execution of their Duty. ITEM, Whereas divers Opinions have been before this Time in what Case Treason shall be said, and in what not; the King, at the Request of the Lords and of the Commons, hath made a Declaration in the Manner as hereafter followeth, that is to say; When a Man doth compass or imagine the Death of our Lord the King, or of our Lady his [Queen or of their eldest Son and Heir; or if a Man do violate the King’s Companion or the King’s eldest Daughter unmarried, or the Wife the King’s eldest Son and Heir; or if a Man do levy War against our Lord the King in his Realm, or be adherent to the King’s Enemies in his Realm, giving to them Aid and Comfort in the Realm, or elsewhere, and thereof be probably] attainted of open Deed by the People] of their Condition: . . . , and if a Man slea the Chancellor, Treasurer, or the King’s Justices of the one Bench or the other, Justices in Eyre, or Justices of Assise, and all other Justices assigned to hear and determine, being in their Places, doing their Offices: And it is to be understood, that in the Cases above rehearsed, that ought to be judged Treason which extends to our Lord the King, and his Royal Majesty" Treason Act 1351 25 Edw 3 St 5 c 2
- 1351 Treason Act 25 Edw 3 St 5 c 2
- Ernst, Kantorowicz (1957). Kings Two Bodies. pp. 78–87.
- Kantorowicz (1957). The King's Two Bodies. pp. 87–97.
- Sidney J, Madge (1938). The Doomsday Of Crown Lands. Routledge. pp. 20–21.
Before the Norman conquest, therefore, it is possible to find a feudal edifice of at least four stages-first, the king as supreme lord;then the holders of "bocland"with their "courts", and the power of making separate grants; next the owners of "laenland", rendering military service and special dues;and lastly, the cultivators of the land (Feudal serfs) of two types, free and unfree.This division of the land before and after the (Norman) Conquest, worked out so carefully in 1867, but expressed in percentage form for the first time, reveals the curious fact that the Church(29.6%) alone gained by the Conquest, relatively speaking, the Crown(19.9%) and the Baronage(50.5%) showing proportionate losses in the new triangular balance of power.
- Kantorowicz, Ernst H (1957). The King's Two Bodies: A Study in Mediaeval Political Theology. Princeton, NJ: Princeton University Press. p. 9. ISBN 0691071209.
- England and Wales High Court (King's Bench Division) Decisions Case of Proclamations  EWHC KB J22 November 1610
- Kantorowicz (1957: 423)
- Olwig (2002: 102)
- Sir William Blackstone (1765) Commentaries On The Laws of England: In Four Books p.196 Volume 1 "But, fourthly; however the crown may be limited or transferred, it still retains its descendible quality, and becomes hereditary in the wearer of it. And hence in our law the king is said never to die, in his political capacity; though,in common with other men, he is subject to mortality in his natural: because immediately upon the natural death of Henry,William, or Edward, the king survives in his successor. For the right of the crown vests, eo instanti, upon his heir; either the hares natus, if the course of descent remains unimpeached,or the hares factus, if the inheritance be under any particular settlement. So that there can be no interregnum (7); but,as Sir Matthew Hale (b) observes, the right of sovereignty is fully invested in the successor by the very descent of the crown.And therefore, however acquired, it becomes in him absolutely hereditary, unless by the rules of the limitation it is otherwise ordered and determined. In the same manner as landed estates,to continue our former comparison, are by the law here hereditary, or descendible to the heirs of the owner; but still there exists a power, by which the property of those lands may be transferred to another person. If this transfer be made simply and absolutely (8), the lands will be hereditary in the new owner, and descend to his heir-at-law; but if the transfer be clogged with any limitations, conditions, or entails, the lands must descend in that channel, so limited and prescribed,and no other".
- The ancient legal maxim is that ‘the King never dies’. According to Blackstone,”the King survives in his successor” and “the right of the Crown vests, eo instanti, upon his heirs”. Thus in legal theory the monarch is regarded as immortal and there is no moment in which the throne is vacant”. Halsbury's Laws of England Fifth Edition Crown and Crown Proceedings pp.8-9 Volume 29 2014
- Butler, John Anthony. James I and Divine Right. Tokyo: Sophia University. p. 14. OCLC 41418652.
- de Baecque (1997: 100–102)