[Sangermaine]

>I am skeptical there will be an 'Event', something more like a gradual decline seems more likely (so, more British Empire than Roman).

I'm not sure what you mean by this. The (Western) Roman Empire's decline was not caused by "an Event" either, it was a gradual process with many causes over several centuries.

[blacksmith_tb]

Yes, we have an overly simple picture of Visigoths etc. - I meant to suggest a scenario where there isn't chaos after empire, just a sort of reduced set of circumstances.