Complex sentence: Britannia Prima was one of the provinces of Roman Britain in existence by c. AD 312 and probably created as part of the administrative reforms of the Roman Emperor Diocletian after the defeat of the usurper Allectus by Constantius Chlorus in AD 296.
Split into simpler sentences: Britannia Prima was one of the provinces of Roman Britain in existence by c. AD 312. It was probably created as part of the administrative reforms of the Roman Emperor Diocletian after the defeat of the usurper Allectus by Constantius Chlorus in AD 296.