Gratian, an Italian monk who taught at Bologna, has been called 'the true founder of the science of Canon Law': his great achievement was to write this work in the mid-12th century. It was the first successful attempt to bring together and reconcile papal decrees which seemed to be contradictory, and to elucidate the general principles on which Canon Law was based. The work was immediately popular and copies such as this one were closely studied and extensively annotated. The three-line inscription at the top of this flyleaf states that this volume was given by John Hereford (corrected to Herefeld, i.e. Harefield), vicar of Plumstead, to the library of St. Augustine's abbey, Canterbury. Below this is a note that the book was bought in 1629 for 20 shillings, and rebound for 4 shillings.