Post-Roman Britain refers to the period in British history from the late 4th to the early 7th centuries AD, following the end of Roman rule. This era, often described as the Early Middle Ages or the Dark Ages, is characterized by a significant lack of contemporary written records, leading to considerable debate and speculation among historians.

Here are some of the key classical and early medieval references that shed light on this period:

1. Gildas’s “De Excidio et Conquestu Britanniae” (On the Ruin and Conquest of Britain): Written in the 6th century, this is one of the few contemporary sources for post-Roman Britain. Gildas was a British monk, and his work provides a moralistic account of British history from the Roman conquest to his own day. He laments the moral decay of the British leaders and the people, blaming them for the disasters that befell Britain, including the invasions of the Picts, Scots, and Anglo-Saxons.
2. Bede’s “Historia Ecclesiastica Gentis Anglorum” (The Ecclesiastical History of the English People): Written in the early 8th century, Bede’s work is a vital source for understanding early Anglo-Saxon history. While it was written much later than the period in question, Bede had access to sources that have since been lost.
3. The Anglo-Saxon Chronicle: This collection of annals was compiled in the late 9th century under the reign of Alfred the Great. It traces the history of the Anglo-Saxons from their origins through to the late 9th century and includes some information about post-Roman Britain.
4. Annals of Wales (Annales Cambriae): A chronicle compiled in Wales, this document records events from the Roman period to the Middle Ages, including some references to the post-Roman period.
5. The writings of Nennius: Traditionally attributed to a Welsh monk in the 9th century, these works include the “Historia Brittonum”, which mixes mythology and fact to tell the history of the British Isles from its founding by Trojan exiles to the 7th century.

This era is marked by the transition from Roman Britain to the various kingdoms that would eventually become England, Scotland, and Wales. It includes the migration and settlement of the Anglo-Saxons and the beginning of their cultural and political dominance in what would become England. The lack of contemporary sources has led to this period being somewhat mythologized, most famously in the legends of King Arthur, which are thought to have their roots in this time.