Britannia Prima

Britannia Prima or Britannia I (Latin for "First Britain") was one of the provinces of the Diocese of "the Britains" created during the Diocletian Reforms at the end of the 3rd century. 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. Its position and capital remain uncertain, although it was probably located closer to Rome than Britannia II. At present, most scholars place Britannia I in Wales, Cornwall, and the lands connecting them. On the basis of a recovered inscription, its capital is now usually placed at Corinium of the Dobunni (Cirencester) but some emendations of the list of bishops attending the 315 Council of Arles would place a provincial capital in Isca (Caerleon) or Deva (Chester), which were known legionary bases.

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. These divided the territory into Upper and Lower Britain (Britannia Superior and Inferior), whose respective capitals were at Londinium and Eboracum (York). During the first phases of the Diocletian Reforms, Britain was under the control of Allectus' Britannic Empire as part of the Carausian Revolt. 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 established and made a part of the Prefecture of Gaul. The Britains were then divided among three, four, or five provinces, which seem to have borne the names Prima, Secunda, Maxima Caesariensis, and (possibly) Flavia Caesariensis and Valentia.

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