Base-silver radiate of the usurper emperor Allectus

Roman Britain, AD 293-296
Probably made in southern England

The second, and last, Roman emperor of Britain

In AD 286, Carausius, a commander in the Roman army, proclaimed himself emperor of Britain, usurping the position of Diocletian, emperor of Rome. In 293, however, Carausius was murdered and supplanted by his finance minister, Allectus. The new usurper then reigned for three years as emperor within Britain.

Why did Allectus take over in 293? Probably because in that year Carausius's armies were defeated in northern France. Diocletian, the senior Roman emperor on the Continent, had also reorganised the government of the Roman Empire, dividing it into two halves with one senior and one deputy emperor in each half. This system is known as the Tetrarchy (rule by four emperors). There was no room within this set-up for Carausius. He was clearly not going to be recognized as a legitimate emperor by Diocletian, so Allectus removed him from the scene.

Allectus proved no better at reconciling Diocletian to his position as emperor in Britain than had Carausius. In 296, the Roman ruler of Gaul (France) Constantius I Chlorus attacked Britain, reannexed it to the Roman Empire and killed Allectus. Thus ended Britain's ten-year spell as a quasi-independent part of the Roman Empire.

P.J. Casey, Carausius and Allectus, the Br (Yale, 1995)

J. Williams and C. Cheesman, Rebels, pretenders and imposto (London, The British Museum Press, 2000)