The Historia ecclesiastica gentis Anglorum, or An Ecclesiastical History of the English People is Bede's best-known work, completed in about 731. The first of the five books begins with some geographical background and then sketches the history of England, beginning with Caesar's invasion in 55 BC. A brief account of Christianity in Roman Britain, including the martyrdom of St Alban, is followed by the story of Augustine's mission to England in 597, which brought Christianity to the Anglo-Saxons. The second book begins with the death of Gregory the Great in 604, and follows the further progress of Christianity in Kent and the first attempts to evangelise Northumbria. These encountered a setback when Penda, the pagan king of Mercia, killed the newly Christian Edwin of Northumbria at the Battle of Hatfield Chase in about 632. The setback was temporary, and the third book recounts the growth of Christianity in Northumbria under kings Oswald and Oswy. The climax of the third book is the account of the Council of Whitby, traditionally seen as a major turning point in English history. The fourth book begins with the consecration of Theodore as Archbishop of Canterbury, and recounts Wilfrid's efforts to bring Christianity to the kingdom of Sussex. The fifth book brings the story up to Bede's day, and includes an account of missionary work in Frisia, and of the conflict with the British church over the correct dating of Easter. Bede wrote a preface for the work, in which he dedicates it to Ceolwulf, king of Northumbria. The preface mentions that Ceolwulf received an earlier draft of the book; presumably Ceolwulf knew enough Latin to understand it, and he may even have been able to read it. The preface makes it clear that Ceolwulf had requested the earlier copy, and Bede had asked for Ceolwulf's approval; this correspondence with the king indicates that Bede's monastery had excellent connections among the Northumbrian nobility.
Divided into five books (about 400 pages), the Historia covers the history of England, ecclesiastical and political, from the time of Julius Caesar to the date of its completion (731). The first twenty-one chapters, covering the period before the mission of Augustine, are compiled from earlier writers such as Orosius, Gildas, Prosper of Aquitaine, the letters of Pope Gregory I, and others, with the insertion of legends and traditions.
After AD 596, documentary sources that Bede took pains to obtain throughout England and from Rome are used, as well as oral testimony, which he employed along with critical consideration of its authenticity. This is impressive; nevertheless, the Historia, like other historical writing from this period has a lower degree of objectivity than modern historical writings. It seems to be a mixture of fact, legend and literature. For example, Bede quotes at length some speeches by people who were not his contemporaries and whose speeches do not appear in any other surviving source; it is doubtful whether oral traditional history supported these ostensible quotations.
The monastery at Jarrow had an excellent library. Both Benedict Biscop and Ceolfrith had acquired books from the Continent, and in Bede's day the monastery was a renowned centre of learning.
For the period prior to Augustine's arrival in 597, Bede drew on earlier writers, including Orosius, Eutropius, Pliny, and Solinus. He used Constantius's Life of Germanus as a source for Germanus's visits to Britain. Bede's account of the invasion of the Anglo-Saxons is drawn largely from Gildas's De Excidio et Conquestu Britanniae. Bede would also have been familiar with more recent accounts such as Eddius Stephanus's Life of Wilfrid, and anonymous Lives of Gregory the Great and Cuthbert. He also drew on Josephus's Antiquities, and the works of Cassiodorus, and there was a copy of the Liber Pontificalis in Bede's monastery.