https://en.wikipedia.org/wiki/Claudius_Gothicus who's reign was pretty late in the Empire phase, though good news for the U.S. it took another 150 years once they started crowning barbarians emperors before it all went to shit. Ironically, it was the emperors from barbarian territory who led the effort to keep second class and first class from mixing; which also rings a little true in our current U.S. political climate.