Ancient Rome: The Rise And Fall Of An Empire.5of6.Constantine (2006, 1080p HD Docudrama)

Starring David Threlfall as Constantine, John Blakey as General Gnaeus and John Woodvine as Lactantius.
This episode tells the story of how the Emperor Constantine brought Christianity to the western world. In AD 312, Rome was in crisis. The empire had been divided into four parts, each with its own emperor who fought one another. Constantine intervened and united Rome, using military might and a new religion - Christianity.