Geoffrey of Monmouth (c. 1100-c. 1155) was a clergyman and one of the major figures in the development of British history and the popularity of tales of King Arthur. He studied at Oxford University, where he met Walter, who was Archdeacon of Oxford. In 1152 Archbishop Theobald consecrated Geoffrey as bishop of St Asaph, having ordained him a priest 10 days before. Geoffrey attested about six different charters between the years 1129 and 1151; the date of his death is recorded in the Welsh Chronicles. He wrote several works of interest, all in Latin, the language of learning and literature in Europe during the medieval period. The earliest one to appear was Prophetiae Merlini (The Prophecies of Merlin), which he wrote at some point before 1135. Next was Historia Regum Britanniae (Histories of the Kings of Britain), the work best known to modern readers. Lastly, Geoffrey wrote the Vita Merlini (The Life of Merlin) at some point between 1149 and 1151.