Carausius in Harpers Dictionary of Classical Antiquities
A native of Gaul, born among the Menapii. His naval abilities
attracted the notice of Maximian, who gave him the command of
a squadron against the pirates. He proved, however, unfaithful
to his trust, and too much bent upon enriching himself.
Maximian thereupon gave orders to put him to death; but
Carausius, apprised of this in season, retired with his fleet
to Britain. Here he succeeded in gaining over, or else
intimidating, the only Roman legion that remained in the
island, and finally proclaimed himself emperor. He forced the
emperors Maximian and Diocletian to acknowledge his authority,
which he maintained for the space of seven years (286-293). He
was assassinated by Allectus.
Read More about Carausius in Harpers Dictionary of Classical Antiquities