Usury, or the practice of lending money at unreasonably high rates of interest, is a criminal activity in my new book, King Richard’s Sword, set in Worcester, England, in 1399-1400. The church banned any charging of interest, and England did not legalise lending with interest until the time of Henry VIII which is more than a century later than my book. As the 14th century was coming to a close, some villains in my novel were able to take advantage of illiterate and poorly educated residents of Worcester to defraud them of significant amounts of their meagre earnings.
The history of usury is ancient. Many important religions have condemned any charging of interest, and some nations have outlawed it in the last three millennia. The Roman Empire did come to legalise lending with reasonable interest. By the 12th century of the Common Era, the Roman Catholic Church banned anyone who took interest on loans from receiving sacraments or Christian burial. Charging any interest was forbidden by church law and could only be done secretly. 
In 1290 the Edict of Expulsion had forced all Jews out of England unless they converted to Christianity with their practice of usury given as the official reason. One of the major characters of the story discovers that his family had been part of this forced conversion.
Usury is an age old problem but one which especially enables two of my villainous characters on both sides monastic walls.
For more information on medieval usury, click on
https://en.wikipedia.org/wiki/Usury or http://www.alastairmcintosh.com/articles/1998_usury.htm .
Tags: Chaucer's England, historical fiction, medieval mysteries