Between AD 244 and 284 the Roman Empire endured tremendous political and economic upheaval. In 284 the emperor Diocletian tried to restore stability by dividing the Empire into a western and an eastern half, each with its own emperor. As part of this effort to bring order back to the Empire, the western emperor Maximian wanted to stop raids made by Saxon and Frankish tribes on the northern coast of Gaul. In 286 he gave the task to Carausius, an admiral of the classis Britannica(Roman navy in Britain).

Carausius was so successful that he was accused by Rome of making money for himself. In order to avoid being executed, Carausius rebelled and declared himself emperor of Britain and Gaul. During the next seven years he was probably responsible for building part of a series of defences around the south and east coasts of Britain, called ‘the forts of the Saxon Shore’. He obviously enjoyed the support of the troops in both provinces and even minted his own coins. In 293 he was assassinated by his finance minister, Allectus, who declared himself emperor. However, in 296 Allectus was defeated and killed by Imperial troops in a battle thought to have taken place near Silchester. Britain was brought back into the Roman Empire and a period of stability followed.