Magnus Maximus in Wikipedia

Magnus Maximus (ca. 335–August 28, 388), also known as Maximianus and Macsen Wledig in Welsh, was Western Roman Emperor of from 383 to 388. As commander of Britain, he usurped the throne from emperor Gratian in 383. However, through negotiation with Theodosius I the following year he was made emperor in Britannia and Gaul - while Gratian's brother Valentinian II retained Italy, Pannonia, Hispania, and Africa. Nevertheless Maximus' ambitions led him to invade Italy in 387, leading to his defeat by Theodosius at the Battle of the Save in 388. His defeat marked the end of real imperial activity in northern Gaul and Britain...