The Roman period, in Britain, led to hundreds of years of peace, but there was a price. A wealthy elite relied on slave labour ,protected by an often foreign born army. Consequently, when the Roman army pulled out, in the 400’s AD, towns and local Government collapsed, This was followed by a remarkable period of anarchy and bloodshed.
Treasure hoards are more common from this period than any other. Desperate wealthy Romans tried to protect their valuables by burying them. Additionally, Judging by how many were never recovered, the scale of devastation can be surmised.
Towns did not recover their former glory for more than a thousand years, as a long dark age began. Medieval towns were disease ridden mires of filth often built on Roman ruins, such as at York.
Hadrian’s Wall AD 122
Hadrian builds a wall
The empire is restored