Heralding the most tempestuous period in the earldom's history, the death of Earl Edmund in 1300 brought to an end the dynasty founded by his father, Earl Richard of Cornwall, king of the Romans. Edmund's patrimony was to pass to his cousin, Edward I himself, creating the link between the lordship and the Crown which endures to this day. For the next thirty-seven years the title bounced back and forth between the king, Piers de Gaveston, Queen Isabella and John of Eltham, before finally returning to the hands of Edward III. It was to this backdrop that in March 1337 Edward elevated the earldom to a dukedom, vesting it upon his son and heir, the Black Prince. In contrast to the previous years of instability, the prince then governed his patrimony assertively for forty years until his death in 1376. In this year, however, Richard of Bordeaux inherited the duchy from his father and in 1377 the lordship came to be vested in the Crown itself after he ascended to the throne of England as Richard II. Although the final disorderly years of the earldom, the punctilious supervision of the prince and Richard's turbulent reign contrast in many ways, together they emphasise the integrative role played by the lordship in Cornwall.

Before embarking on the fourteenth-century history of the earldom-duchy, however, it is worth considering what expectations contemporaries had of good lordship. According to Robert Boutruche, lordship, dominium, was the ‘power of command, constraint and exploitation. It [was] also the right to exercise such power’. The institution of lordship emerges as ubiquitous in medieval England. Even Cornwall's miracle plays were infused with the lordly language of fiefs and liege lords, with the character of Christ himself stating that lords enjoyed ‘dominium over their people’ (myghterneth war aga tus). Yet despite the power of lordships great and small across England, a profound difference existed between the mere exercise of power and actual ‘good lordship’.

To aid this analysis we can separate the lord's perspective of good lordship from that of his dependants. The former can perhaps best be summarised as involving effective governance and correct behaviour. In his treatise on estate management, Walter of Henley recommended that a lord should thoroughly acquaint himself with his patrimony.