In 410 AD the last Roman soldiers left Britain and they never came back. Roman Britain was at an end.

Most of Britain had been part of the Roman Empire for almost 400 years. But by the end of the 4th century that Empire was in trouble. 

Rome's glory had been built on conquering other peoples and buying, selling and stealing things from their lands. Goods brought to Rome included metals such as gold, silver, copper and tin, textiles, pottery, and building materials such as stone, marble, wood and bricks, not forgetting the huge trade in slaves, captured peoples, on which the Empire depended.

This could not last.

With no new lands to conquer, the army (a quarter of a million strong) could not be paid to protect the Empire. Soldiers stole from the people or left the army to become outlaws. Foreign soldiers were paid to fight for Rome but they were unreliable. 

The civil service and the great public buildings in the cities across the Empire could no longer be paid for. Temples, baths and other public buildings were not repaired and they fell into ruins. The Roman roads were not mended. Taxes were increased but people could not afford to pay them. 

And Rome's enemies were getting stronger, especially the tribes of Germans and Goths in central Europe on the borders of the Roman Empire.

In 410 AD Alaric, the King of the Visigoths successfully attacked the city of Rome itself. 

In 410 AD the Roman army in Britain was called back by the Emperor

to defend Rome.

Britain was Roman no longer.

So what happened next?

It just got worse . . .