One of the fundamental elements of Christine Carpenter's work, and a theme that weaves its way through the pages of Locality and Polity, is ‘the intermingling of private and public’ in fifteenth-century England. On the one hand, ‘commentators on the late medieval body politic stress precisely that quality implied in this corporeal metaphor: the oneness, the unity that is greater than the sum of its parts’. On the other, ‘there is scarcely a governmental measure that can be assumed to be determined by disinterested bureaucratic procedure’. The history of the Duchy of Lancaster in the fifteenth century provides one of the most remarkable examples of ‘the intermingling of private and public’. On his accession in 1399 Henry IV provided expressly that the lands of the Duchy should remain private estates within his hands, ‘as if we had never achieved the height of royal dignity’. By contrast, in 1461 Edward IV's first parliament ordained that following its forfeiture by Henry VI, the estates of the Duchy should make

The Duchy was thereby made part of the permanent possessions of the crown but as a separate institutional entity – ‘the Duchy of Lancaster corporate’ – and so it has remained until today.

Exactly a century after its ‘incorporation’ the Duchy was the subject of a legal cause célèbre recorded in the Reports of Edmund Plowden, the Elizabethan lawyer. The Case of the Duchy of Lancaster, argued in court in 1561, arose from a lease of Duchy lands made by King Edward VI while he was not yet of age. In normal circumstances a landowner's minority would have invalidated the grant. However, Queen Elizabeth's judges decided that Edward VI's position as king overrode his legal incapacity as a minor. Edward's ‘body natural’ was inseparably linked to his ‘body politic’ as king. In explanation of this the judges set out the classic statement of the doctrine in English law of the king's two bodies. This is the fiction that the king is both a body politic, which never dies, and a mortal body natural.