prior to its recapture, Britain enjoyed the best of both worlds as a unified and isolationist nation-state that could still claim affinity with the greater dominion of Rome across the Straits of Dover
Sounds familiar...
By the way, I remind you that civilisation was brought to Great Britain by a man from Lyon... "Ce qui vient au monde pour ne rien troubler ne mérite ni égards ni patience." René Char
They also seemed to have learned a valuable lesson; when Severus went north of Hadrians wall on a punitive mission they declined to meet him in open battle. Instead they attacked his foraging crews and supply trains, eventually starving him back south. A tactic that appears to work just as well nowadays. keep to the Fen Causeway
Carausius - Wikipedia
Coinage is the main source of information about the rogue emperor; his issues were initially crude but soon became more elaborate and were issued from mints in Londinium, Rotomagus and a third site, possibly Colonia Claudia Victricensis.
Rotomagus is today's Rouen, France.
I also note that just a few decades prior, 260-274, there was another three-way split, during which time Britain was part of the Gallic Empire... *Lunatic*, n. One whose delusions are out of fashion.
