Celts in BritainThe Celts were European that lived all across northern and western and south eastern Europe and Celtic was their language. Besides, Celts were divided in different tribes: The Brithons and the Gaels. They lived in closely tied clans and were farmers and hunters.Their leaders were Druids, who were priests. They preserved myths and legends by reciting long, heroic poems because they did not have a form of writing at that time. So, all literature, history and law had to be remembered by them.
The Roman InvasionRomans invaded England and then ruled for about 300 years. Their contribution to England were primarily in the form of roads and towns which continued to be used and inhabited today.
Roman rule in Britain endsTheir rule ended because Italy was under attack from northern invaders and these were also Germanic or Celtic tribes called vandals and the Visigoths. Basically, the troops were called home to defend homeland and that left England open for the Anglos and the Saxons. The last troops left in 407, and the stage was set for Anglos and the Saxons. They brought Christianity to the island.
The Anglo-Saxon InvasionBritain was invaded by The Angles, SaxonsJutes, Picts, Scoti, and the Gallic from Ireland.They were able to over take the Britons by simply rowing up English rivers.
Anglo-Saxon ruleThe Britons went to the edges of the island -- Cornwall and Wales. Others went to Ireland and then later Scotland. This movement proved to preserve the Celtic languages of Cornish, Welsh, and Irish and Scottish Gaelic. All of which are spoken today
The Danish (Viking) InvasionsEnglish king Alfred the Great was able to resist the first invasion. The Vikings ended up practicing "hit-and-run" raids, but their influence was not large.