Map of the Roman dioceses
The Diocese of Britain was a regional administrative district of the Roman Empire which was created during Diocletian's reforms during his reign from 293-305 AD. Following the Edict of Milan in 313 AD, the Christian Church was legalized, and it created dioceses in every Roman province; these existed until the late 5th century. The Diocese of Britain covered England, Wales, and parts of southern Scotland, consisting of four Roman provinces; it was swept away by invading barbarians during the 410s.