“The establishment of the Chancery of Westminster in the 1430’s set standard spellings for official state documents. In…
“The establishment of the Chancery of Westminster in the 1430’s set standard spellings for official state documents. In particular, the use of ‘I’ in preference to ‘ich’ and a variety of other usages of the first person pronoun. The spelling of other words such as ‘land’ (the 'lond’ of Chaucer) also became standardized in the modern form, alongside words like 'such,’ 'right,’ 'not,’ 'but,’ 'these,’ 'shall,’ 'should,’ and 'could’. The influence of Chancery Standard was keenly felt in the quest to develop Standard English. The East Midlands dialect had gained cultural dominance over the other dialects and flowed in through the political, commercial and cultural 'triangle’ that joined London, Oxford and Cambridge. However, the advent of the printing press and mass publication necessitated further developments in the standardization process. The Chancery clerks had adopted the East Midland variants, and this naturally rubbed off on the London print houses. Some choices made by printers seem to have been quite arbitrary, however. For example, the adoption of the Northern dialect form 'they,’ 'their’ and 'them’ for plural and possessive pronouns, when the more common Southern dialect favoured 'hi,’ 'hir’ and 'hem’ (although this may have been simply to create a clear distinction with singular pronouns such as 'he,’ 'her’ and 'him’). …Early proof readers must have had a near-impossible task, as books often contained multiple variations of spellings of the same word. Particular confusion centred on the use of double vowels and consonants; for example, 'booke’ and 'boke’ and 'fellow,’ 'felow’ and 'felowe’. …Punctuation was another area in which usage and forms gradually became more standardized through printed language. Full stops became common at the end of sentences, and the convention of using capital letters for proper nouns and at the beginning of sentences became commonplace.”— “The Story of English: How an Obscure
Dialect Became the World’s Most-Spoken Language” (via mostly-history)