43 CE

The Roman conquest of Britain begins. Emperor Claudius (10 BCE–54 CE) orders the invasion of the British Isles, sending forces commanded by Aulus Plautius (15 BCE–57 CE). The province of Britannia is established.

c. 214

Britannia is divided into two provinces—Britannia Superior and Britannia Inferior.

296

Emperor Diocletian (245–316 CE) renames the entire area the Diocese of Britannia and further divides each province in two, thus forming four provinces—Britannia Prima, Maxima Caesariensis, Britannia Secunda, and Flavia Caesariensis.

410

Emperor Honorius (384–423 CE) refuses to aid the civitates of Britain, thereby implicitly ending Roman rule.