It is the 6th century.
The Western Roman Empire has been overrun by Germanic barbarians and has collapsed. We’re looking at the aftermath as the Franks spill over the Rhine and begin to conquer northern Gaul. Clovis unites all the Franks under his rule, converts to Christianity and forces his subjects to convert. By the 7th century, the Franks rule most of France and western Germany.
Shortly after the Romans withdraw from Britain in 410 AD, the Anglo-Saxons arrive no later than 450 AD and begin the conquest of what is now England from which they carve out the seven Anglo-Saxon kingdoms of Kent (Jutes), Wessex, Essex, Sussex (Saxons), East Anglia, Mercia and Northumbria (Angles). Hengist and Horsa were Jutes who established the first beachhead in Kent in the far southeast of England where there was a catastrophic collapse of Roman civilization in the 5th and 6th centuries. It must have resembled a post-apocalyptic wasteland.
Genetically speaking, Britain is largely unchanged down to the present day and still resembles what it looked like in 600 AD. This was the beginning of a huge cultural change though because it was around this time that the Anglo-Saxons began to convert to Christianity.
There were four factors that converged here:
- The first was that Francia had stabilized into a Catholic kingdom under the Merovingian dynasty. Earlier in the late 5th century, Clovis had converted to Christianity through his wife. It happened again when Æthelbert of Kent married Bertha, a Christian daughter of the king of Franks, and converted to Christianity himself through family ties with the most powerful kingdom in Western Europe.
- The second was Gregory the Great who had developed a longtime interest in the conversion of the Anglo-Saxons.
- The third was Augustine of Canterbury who was sent on the mission to evangelize the Angles and Saxons by Gregory and became the first Archbishop of Canterbury after establishing the first Christian beachhead in England in Kent.
- The fourth factor was Irish missionaries coming in from the north who converted Northumbria to Celtic Christianity.
The Anglo-Saxons kingdoms converted to Christianity in the 7th century. In the late 9th and early 10 centuries, King Alfred and his successors created a unified Christian England in response to the Viking invasions. Shortly thereafter, England was conquered by the Danes and Normans and by that point we are in the High Middle Ages which is a different era.