Marcus Aurelius Mausaeus Carausius
Emperor of Roman Britain (286-93)
Carausius was born sometime in the mid third century and is believed to have been a citizen of the city of Menapia, (in what is now Holland), although he may well have been born elsewhere, perhaps even in Britain.
Other than the fact that he had naval experience not much is known about him until the year 284 when he served in Gaul under Maximian (who at that time was the emperor Diocletian's Caesar, or deputy) whilst the latter was surpressing the revolt of the Bacaudae. Although the revolt itself was put down by 286, serious problems remained on the north coast of Gaul due to the activities of Frankish and Saxon pirates. Carausius was therefore given command of the Roman naval fleet based in the port of Gesoriacum (modern Boulogne) with the specific task of clearing the channel of these pirates.
However it wasn't long before Maximian (who had by now been promoted to Augustus by Diocletian, and therefore had effective control of the western Roman Empire) ordered the arrest of Carausius for alleged financial irregularities. The specific allegation was that, rather than taking action to prevent such raids, Carausius was intercepting the pirates on the return leg, seizing their booty for himself and making no attempt to either return it to its rightful owners or handing it over to the imperial authorities. (One suspects that the latter would have been considered the greater crime.)
We have no idea of the truth behind these charges, Carausius may well have taken the opportunity to enrich himself, but it is equally possible that Maximian had received some intelligence of Carausius' intentions and plans and simply invented a convenient pretext for his arrest.
The empire of Roman Britain
Carausius reacted by relocating himself, together with his fleet and the troops under his command to Britain and declaring himself emperor. Precisely how Carausius managed to take control of Britain is not recorded as there are no real contemporary records of events. It is reasonably certain that he managed to win the support of the Roman Army in Britain (since no one got anywhere in thosedays without military support) and it is likely that he had at least some degree of support from the Romano-British nobility and the acquiescence of many more.
He seems to have made no attempt to challenge the position of Maximian or Diocletian as rulers of the Roman Empire itself, and appears to have been content to have ruled the provinces of Britain together with an undetermined area of northern Gallic coast (including at least the area around Gesoriacum).
Since he had the entire Roman channel fleet under his command, neither Maximian or Diocletian was in a position to challenge his authority until they had contructed a fleet of their own. By 289 preparations for an invasion of Britain were well advanced before the invasion fleet was severely damaged by a storm. Without the necessary ships Maximian was unable to challenge Carausius's command of the channel and with pressing problems elsewhere he and Diocletian were forced to formally acknowledge Carausius in a peace treaty.
Coinage as propoganda
As background it should be noted that during the third century the Roman state had effectively ceased to issue gold and silver coinage in any significant quantity. Most of the coin in circulation (particularly in Britain) was of a low quality. Much of this was due to the political uncertainties of the period; twenty two emperors ruled in the years between 235 and 284 and much of the western empire (Gaul, Iberia and Britannia) had been seperated in the independent Gallic Empire between 260 and 273.
When Carausius seized power in 286 one of his first actions was to order the minting of new gold and silver coins. The silver coinage he minted was, at 90 percent purity, to a standard unknown since the time of Nero, over two centuries before, outdoing anything that the legitimate emperors could produce. (And of course, it was perfectly possible that he had a ready source of bullion in the form of the loot that he had previously obtained.)
This in itself was a powerful claim to legitimacy but coinage was also produced including designs that specifically presented Carausius as the restorer of traditional Roman values, proclaiming him as the 'restorer of the Romans' and 'the awaited one'.
Many of the coins displayed the letters RSR which are now believed to be derived from the initial letters of the phrase Redeunt Saturnia Regna, a line from Virgil's Fourth Eclogue, which literally transalates as 'The return of the reign of Saturn' and is a reference to the myth that once there had been a paradise on earth ruled by the god Saturn. There is also an example of a bronze medallion bearing the letters INPCDA, which seems to refer to the next line in the Fourth Eclogue, which reads Iam Nova Progenies Caelo Demittitur Alto and means 'Now a new generation is let down from heaven above'.
It therefore seems as if Carausius was presenting himself as a saviour figure to the Romano-Britons, appealing to traditional Roman pagan religious values, and offering the prospect of re-establishing some kind og golden age of prosperity. It is presumably for the same reason that he also assumed the forenames Marcus Aurelius in order to deliberatly associate himself with Emperor Marcus Aurelius. Carausius was posing as the ultimate legitimate Roman ruler in a context which will have outraged .
The end of Carausius
In 293 both Diocletian and Maximian appointed two new Caesars as their heirs and assistants, respectively Galerius and Constantius Chlorus, thereby establishing what has since been known as the Tetrarchy. Constantius Chlorus was given the task of recovering Britain and later in 293 he blockaded the harbour at Gesoriacum and forced the city to surrender.
The loss of Gesoriacum and the northern coast of Gaul seems to have precipitated a coup in Britain; Carausius was assassinated and replaced by one Allectus who then declared himself emperor in Britain. Fortunately for Allectus, Constantius Chlorus had more pressing matters on the Rhine frontier to deal with and wasn't yet in a position to invade.
Postscript - Britain reunited with Rome
With the Gallic coast now under his control Constantius Chlorus spent the next two years preparing for the attack across the Channel. By 296 he was ready, and Maximian moved to the Rhine to guard the frontier whilst the invasion went ahead.
The invasion fleet was divided into two squadrons; the first was commanded by Constantius Chlorus himself, the second was commanded by the praetorian prefect Asclepiodotus. They succesfully managed to evade detection by the British fleet, but Constantius Chlorus was prevented from landing by bad weather. Asclepiodotus howver landed somewhere on the Hampshire coast, marched rapidly inland, caught up with Allectus and fought a battle in which Allectus was defeated and killed. When Constantius Chlorus finally disembarked he was therefore able to simply march into Londinium, recover the capital and re-establish imperial authority in Britain.
Peter Salway Roman Britain Oxford University Press (1991)
Together with http://www.roman-emperors.org/carausiu.htm but particularly http://www.bedoyere.freeserve.co.uk/carausius.htm from which most of the information regarding Carausian coins was drawn.