Britannia Inferior was a new province carved out of Roman Britain probably around AD 197 during the reforms of Septimius Severus although the division may have occurred later, between 211 and 220, und
Hadrian's Wall, the northern border of Britannia Inferior
Flavia Caesariensis, sometimes known as Britannia Flavia, 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
Roman Britain around AD 410, without speculative provincial borders.
The traditional arrangement of the late Roman provinces after Camden, placing Flavia in central England. On the basis of modern archaeology, it's known that at least Corinium was part of Britannia I.