For nearly 200 years after the Romans left in 410 AD, Britain had no written word.
It must have been incubation, because starting around 600 AD it exploded.
Rome civilized Britain.
I wholeheartedly agree. About the only viable counterargument is that the earlier coat of paint that, long before, had built megalithic monuments such as Stonehenge, was trampled to death by the later wave of migrants. Hmm, that sounds familiar.
It's interesting that the Romans built an 80 mile canal to drain swampy areas in the middle of what later became England, which was also intended for and used as a transportation link, in the 1st century, and that Roman settlements as well as Romanized locals thrived for hundreds of years. In some places they lingered on, or reemerged, during the Angle/Saxon/Jute invasions, and even later when the Danes arrived.