Britannia Inferior
Britannia Inferior (Latin for "Lower Britain") was a new province carved out of Roman Britain around  197 during the reforms of Septimius Severus. The removal of the governors in Londinium from control over the legions guarding Hadrian's Wall was aimed at reducing their power, given Clodius Albinus's recent bid to become emperor. The province was probably formalised around 214 by Severus's son Caracalla.

Including much of modern northern England, as well as the area that is now Wales, the region was governed from the city of Eboracum (modern York) by a praetorian legate in command of a single legion stationed in the city. This subdivision of Britannia lasted throughout the Severan dynasty until the reorganisation of the empire under Diocletian in 296.

Establishment
During the reign of Commodus, the defences along the northern border of the empire in Britannia fell into neglect and disrepair.  The peace of the region was further disturbed in the tumultuous period after Commodus' death as the military power vacuum on the continent distracted the defensive legions stationed in Britannia. After his accession in 193, Severus took special interest in refortifying the northern border in Britannia, and in 208 he moved to Eboracum to oversee the military campaigns against the northern tribes. While there is some confusion as to the exact date when the subdivision of Britannia was made, it seems clear that Severus's intentions were to break up the size of the military under the command of an individual governor (as he had done in Syria), preventing them from wielding too large a military force, or at least one that could destabilize the emperor's control. Herodian puts the date of the split in 197, although there is no evidence of this distinction being formalised in inscriptions until after the death of Severus in 211. Thus, it is likely that the division of military control in Britannia was formally established by Caracalla sometime between 211-20.

Reorganisation
In 296, the emperor Diocletian conducted a major reorganisation of the empire. The newly named Diocese of Britannia was subdivided into four provinces, Britannia Prima and Maxima Caesariensis from Britannia Superior and Britannia Secunda (capital in Eboracum) and Flavia Caesariensis (capital in Lindum) from Britannia Inferior.