Magnus Maximus
Magnus Maximus (c. 335 - July 28, 388) was emperor of the western Roman Empire from 383 AD until his death in 388.A Spanish Celt, Maximus was proclaimed emperor by his troops in 383, while serving with the army in Britain. His main opponent, Gratianus, was defeated near Paris and, after fleeing, was killed at Lyons on August 25, 383. Maximus made his capital at Augusta Treverorum (Treves, Trier) in Gaul. A devout Christian, he was a popular emperor, although also a stern persecutor of heretics.
According to the Mabinogion, Magnus Maximus (in Welsh, called "Macsen Wledig") took as his wife Helen or Elen, daughter of a chieftain based at Segontium (Caernarfon). Although the story of their meeting is undoubtedly fictional, there is some evidence for the basic facts. Welsh legend also claims that he was responsible for the withdrawal of Roman troops from Wales, twenty years before the rest of Britain was left to govern itself.
Magnus Maximus was defeated, captured and executed by Theodosius I, along with his son.