I suspect it was bigger than the South Bank Empire that I used to go to as a lad on Friday evenings with my parents...
Seriously, the Romans had their day, to be replaced by the Holy Roman Empire in the west and the Byzantine Empire in the east of Europe. Established after several bitter battles by Constantine, made emperor at Eboracum just before the Romans left Britain in AD 410, the Eastern Empire fell prey to 'new technology', i.e. gunpowder used by the Turks in 1453..
Their empire was overstretched for the poor means of communication they had then, just as the Greek Empire before them faltered after Alexander's demise.
'Every dog has his day' also applies to us (Britain), the Danes, the French, the Spaniards, the Dutch, the Portuguese, Austrians... Germans, Japanese, Russians.
Who's next in the queue for Armageddon, the Chinese ?or the US?