Boek 6, 5, 2-3

The barbarians beyond the Rhine, attacking in force, reduced the in­habitants of Britain and some of the Celtic tribes to the point where they were obliged to throw off Roman rule and live independently, no longer subject to Roman laws. The Britons therefore took up arms and, braving the danger on their own behalf, freed their cities from the barbarians threatening them. And all Armorica [Brittany] and the other Gallic provinces followed their example, freed themselves in the same way, expelled their Roman rulers and set up their own governments as far as lay within their power.

Boek 6, 10, 2

Honorius wrote letters to the cities in Britain bidding them to take precautions on their own behalf.