As I said in another comment, just bear in mind the possibility that the map of 878 England from the 19th century could well be based upon the same evidence. A

As I said in another comment, just bear in mind the possibility that the map of 878 England from the 19th century could well be based upon the same evidence. Although it is significant that the names survive and show clear boundaries, it may well be a lot less significant that a modern map and a 19th century map show the same boundaries.