This thesis closely analyses the linguistic forms of aspects of non-royal charters produced c.1066-c.1250 in the north-east of England and the south-east of Scotland, namely, consent, joint grants, separate confirmations, inheritance language, leaseholds and warranty. This study identifies the preferred forms of each studied aspect as well as variants, developments and alternatives and analyses them according to a clear chronological framework and other potential causal factors such as the status and gender of participants, location and grant type. Additionally, the spread of linguistic patterns throughout the studied region, Stringer's “diplomatic transplant”, is examined. Firstly, the charter underwent tremendous development across this period of study becoming trusted evidence of landholding transactions routine at most levels of society and subjected to sophisticated scrutiny by legal professionals in landholding disputes. Secondly, charter language was introduced, modified or abandoned according to many influences, e.g. the emergence of early Common Law systems in both Scotland and England, the rise of the legal profession and the growth in written culture evidenced partly through the spread of monastic houses and increasing trust in the written word. Indeed, the introduction of significant legal reforms – in England from the 1160s and in Scotland during the second quarter of the thirteenth century – are repeatedly revealed to be the point at which linguistic patterns became noticeably more settled and variants became much rarer. Notably, the fact that the language patterns of the Northumberland houses better mirror the patterns seen in south-east Scotland demonstrates the contrast in the level of bureaucratic organisation against the neighbouring shires of Durham and Yorkshire. Thirdly, this thesis highlights the existence of preferred linguistic forms by individual religious houses, religious orders, families or groups of people within localities or larger geographical regions. In particular, religious houses were especially influential in the widespread adoption of some forms of language. Overall, developments and changes to charter language were streamlined, revised or modified with the dual aims of providing greater clarity and thus maximum legal protection; before legal reform the latter was much more dependent upon familial and seignorial ties, a factor reflected in the greater variety of linguistic forms.