The Roman army and generals had left by 407AD. Britons were on their own. No more taxes to pay, hurrah. No more being a slave in
a villa, hurrah. No one to run the country efficiently, hur..ooops. No one to stop invaders, double ooops. England now returned to how it was almost 400 years ago
with tribal warfare. Towns disappear and people go back to living in the countryside.
In 401, the estimated population of England (to the nearest ¼million) was 2 million people.