Great English dates No 1: AD 410

What are the key dates in English history? Simon Jenkins kicks off a new series with the year when the Roman empire abandoned Britannia to its own fate

The true first date in English history is AD 410. That year, a letter was sent from the western Roman emperor, Honorius, to his desperate colonists in Britannia, under attack from Anglo-Saxon raiders and pleading for help. Honorius refused. They were on their own.

There are two theories of what happened next. Most historians think that...