Historians in England during the Middle Ages helped to lay the groundwork for modern historical historiography, providing vital accounts of the early history of England, Wales and Normandy, its cultures, and revelations about the historians themselves. The most remarkable period of historical writing was during the High Middle Ages in the twelfth and thirteenth centuries, when English chronicles produced works with a variety of interest, wealth of information and amplitude of range. However one might choose to view the reliability or nature of particular works, it is from these that much of our knowledge of the Middle Ages originates. Early Middle Ages Prior to the boom in historical writing in the High Middle Ages, the number and quality of works from England's earlier period is often lacking, with some notable and bright exceptions. Later historians lamented the gaps in this period and usually explained it by way of Viking invasions; in the twelfth century William of Malmesbury said: "in many places in England that knowledge of the deeds of the saints has been wiped out, in my opinion by the violence of enemies". Listed chronologically, by author's death. Dates represent the historical period covered by the work(s). Works and authors listed are not exhaustive. Here are the major and most significant historians and chroniclers of the period: Gildas, On the Ruin of Britain (De Excidio Britanniae) (died 570) Bede, Ecclesiastical History of the English People (Historia ecclesiastica gentis Anglorum) AD 1-731 History of Britain (Historia Brittonum) 809 (attributed to Nennius, perhaps falsely) Asser, Life of King Alfred 893 Annales Cambriae, Annals of Wales 447-954 (c.970) Æthelweard, Chronicle (Chronicon Æthelweardi) AD 1-975 High Middle Ages The High Middle Ages were a golden period for historical writing in England. The craft of history was not a professional subject taught in school, such as the scholastic subjects of logic, theology, law and natural science, but rather something practised by well-educated men of learning, not subjected to the process of systems and procedures of Academia. It was a realm for educated men in monasteries and the courts of kings, bishops and barons, who had the time and position and particular talents to pursue it. As a result, the quality and variety of the histories from this period are highly variable, with some entertaining and appealing examples. Numerous chroniclers prepared detailed accounts of recent history. King Alfred the Great commissioned the Anglo-Saxon Chronicle in 893,