 The "History"'s effect on the legend of King Arthur was so vast that Arthurian works have been categorised as "pre-Galfridian" and "post-Galfridian", depending on whether or not they were influenced by him.Geoffrey wrote several works in Latin, the language of learning and literature in Europe during the medieval period.His major work was the "Historia Regum Britanniae" ("The History of the Kings of Britain"), the work best known to modern readers.