1. Late Pre-Roman Iron Age

The last centuries before the Roman invasion saw an influx of refugees from Gaul (modern day France and Belgium) known as the Belgae (their name survives in modern Belgium), who were displaced as the Roman Empire expanded.

It seems likely that the Belgae had a mixture of Celtic and Germanic ancestry. Perhaps they were Germanic people ruled by a Celtic élite, or were a political alliance of Celtic and Germanic tribes, or, like the later Normans, were a formerly Germanic-speaking people who had adopted the language of the lands into which they migrated. From around 175 BC they settled in the areas of Kent, Hertfordshire and Essex and brought with them pottery making skills far more advanced than anything produced previously. The Belgae were partially Romanised and were responsible for creating the first settlements large enough to be called towns.

The last centuries before the Roman invasion saw increasing sophistication in British life. About 100 BC, iron bars began to be used as currency, while internal trade and trade with continental Europe flourished, largely due to Britain's extensive mineral reserves. Coinage was developed, based on continental types but bearing the names of local chieftains.

As the Roman Empire expanded northwards, Rome began to take interest in Britain. This may have been caused by an influx of refugees from Roman occupied Europe, or Britain's large mineral reserves.

2. The End of Iron Age

Historically speaking, the Iron Age in Great Britain ended with the Roman invasion. In areas where Roman rule was not strong or was non-existent, Iron Age beliefs and practices continued for centuries. Even in southern Great Britain, earlier place names survived indicating that Latin ways had not entirely removed the pre-Roman culture. But the invaders introduced new developments in agriculture, urbanisation, industry and architecture, leaving a legacy that is still apparent today.

Roman Britain refers to those parts of the island of Great Britain controlled by the Roman Empire between 43 and 410. The Romans referred to their province as Britannia. The name "Britain" comes from the word "Pretani", the Greco-Roman word for the inhabitants of Britain. The Romans mispronounced the word and called the island "Britannia". The word also got associated with Celtic goddess Brigid, Dagda’s daughter.

The Romans had invaded because the Celts of Britain were working with the Celts of Gaul against them. The British Celts were giving them food, and allowing them to hide in Britain. There was another reason. The Celts used cattle to pull their ploughs and this meant that richer, heavier land could be farmed. Under the Celts Britain had become an important food producer because of its mild climate. It now exported corn and animals, as well as hunting dogs and slaves, to the European mainland. The Romans could make use of British food for their own army fighting the Gauls.

Historical records beyond the initial invasion are sparse, although many Roman historians mention the province in passing. Much of our knowledge of the period stems from archaeological investigations and especially epigraphic evidence.