[1] It was probably created after the defeat of the usurper Allectus by Constantius Chlorus in AD 296 and was mentioned in the c. 312 Verona List of the Roman provinces.
Following the Roman conquest of Britain, it was administered as a single province from Camulodunum (Colchester) and then Londinium (London) until the Severan Reforms following the revolt of its governor Clodius Albinus.
At some point after the territory was retaken by Constantius Chlorus in AD 296, the Diocese of the Britains (with its vicar at Londinium) was formed and made a part of Prefecture of Gaul.
[b][4][5] The placement and capitals of these late British provinces are uncertain, although the Notitia Dignitatum lists the governor (praeses) of Britannia II as being equestrian rank, making it unlikely to have been based in Londinium.[why?]
Ammianus records that in the year 369 Count Theodosius established or refounded the province of Valentia (further attested in the List of Offices) from lands recaptured from "the enemy".