Which English reformer called for change in the church during the 1300s?

As the medieval world entered its late phase in the 1300 and 1400s, English society (and indeed, the society of all Europe) began to undergo a rapid transformation.

After England began to recover from the worst bouts of the Black Death, the economy improved along with general health and a middle class began to emerge, especially in the towns. Literacy was spreading among the top economic half of the populace and as life improved many people began to have a little more leisure time for reading and writing, especially personal documents such as letters.

English became the language of the law courts in 1362 for the first time since the Conquest, and a clerk class had to be educated in written English for purposes of administering the business of the courts. The royal court and its legal administration were based in London and London duly became the hub of a newly developing Standard English, both spoken and written.

The development of legal and administrative English further encouraged the spread of literacy in English. At the same time public readings of poetry and stories became popular, at first especially in French, but written stories and poems in English also began to appear in the 1300s. Geoffrey Chaucer, a well-connected courtier and civil servant, began writing in English in the 1380s, starting a new trend for creative literature in English instead of French.