The Duchy of Cornwall
Edward III created the Duchy of Cornwall as an estate for the Black Prince; A.L. Rowse describes how it has been held ever since by the sovereign’s heir or lain dormant in the Crown.
The Duchy of Cornwall is a peculiarly interesting institution, with a constitutional status and characteristics all its own, of which few people are aware and with which only a few lawyers are competent to deal. It is first necessary to clear out of the way the popular confusion between the Duchy and the county of Cornwall. They are two entirely separate entities, utterly differing in character.
The one is an ordinary - or to a Cornishman, a not so very ordinary - county, as it might be Devonshire or Dorset; whereas the Duchy is an institution, an aggregation of estates vested in the eldest son of the Sovereign (or, in the absence of a son, lying dormant in the Crown). It has been based from time immemorial upon extensive lands in Cornwall, and has existed as a duchy, save for the interregnum of the Commonwealth period, since 1337.