Who composed 'The History of the Kings of Britain'?

Geoffrey of Monmouth (Latin: Galfridus Monemutensis) was a British cleric and one of the major figures in the development of British historiography and the popularity of tales of King Arthur. He is best known for his chronicle The History of the Kings of Britain which was widely popular in its day, being translated into other languages from its original Latin. It was given historical credence well into the 16th century, but is now considered historically unreliable.