An Earlier Brexit in the 3rd Century
Carausius, full name (as from a milestone found at Carlisle) Marcus Aurelius Mausaeus Valerius Carausius, was not even a Roman despite his name. He was a Celt from Gaul (Northern France). Yet he rose, from humble beginnings, to command the Roman Channel Fleet, Classis Britannica, and finally to declare himself Emperor of Britain and Northern France.
Declaring himself Emperor in 286 was rather forced upon him, because he had been caught out in a scam as Commander of the Fleet. The Fleet's purpose was to keep The Channel free of pirates. Carausius was accused of letting the pirates capture merchant shipping before attacking them. He would then redirect a substantial part of the pirates' loot to his own use. He was tried in absentia and sentenced to death. That was his spur for rebelling. Yet there must have been enough support in the Army and amongst the civilian population for this ever to have succeeded. For succeed it did, when sailing his fleet north Carausius defeated Britain's Roman Governor, Quintus Bassianus, near York.
Carausius ruled until 293, although in 288 or 289 he had to defend his gains against legitimate imperial forces. He won a victory, or so he claimed, other sources suggest bad British weather drove the invading forces back to the continent.
Written sources for his reign remain thin on the ground, and are almost entirely biased against him. The best source is from the large coinage he issued from three mints, London, Rouen, and a third, which some believe was Colchester. He issued silver and gold coins in addition to the normal bronze. The inscriptions on the coins are most illuminating. On one series Carausius is described as 'Ruler of The North', somewhat reminiscent of 'Game of 'Thrones. In others he is described variously as 'Restorer of Britain', 'Spirit of Britain', and with a quotation from The Aeniad as 'Come thou long awaited one' (Expectate Veni), with a picture of Carausius being warmly embraced by Britannia. Very Dominic Cummings!
Roman coins, unlike subsequent Saxon and Medieval ones, (until the reign of Henry VII), did not portray real likenesses of the kings who issued them. But from Carausius' coinage we can see very clearly that with a large head and a thick bullish neck he looks more like a bouncer than a classical Roman Emperor.
If you are a usurper you give other people the idea too. Allectus, who was Carausius's Treasurer, was one such, and in 293 he assassinated Carausius and assumed the British 'throne'. He only lasted three years until an imperial army, under The Praetorian Prefect, Julius Asclepiodotus, landed on the Isle of Wight and defeated and killed Allectus at a battle at Silchester.
A brief moment of independence from Rome. Were ordinary Britons better off being ruled by a Celt? Rather unlikely and there is no evidence for that. Did trade collapse? Little evidence that it did. Did ordinary Romano-Britons celebrate with street parties? No. In fact it is probably more accurate to say people really didn't care much. After all it was only politics. Provided there was no military threat or economic meltdown, people just carried on in a rather British way. The elite on their luxury villa estates, the poor on the land, as ever scratching a living.