The Roman invasion was the first of Britain's historically recorded invasions: Julius Caesar himself wrote a laconic and somewhat ambiguous account of his two campaigns of 55 and 54 b.c. But this well-publicized invasion was only one of many unrecorded sporadic incursions into southern Britain, which had by that time been completely overrun by tribes coming from the Continent. Archaeological evidence has now revealed the long painful periods of the Iron Ages known as A, B and C, when southern Britain with her small but effective barrier of the Channel and its dangerous tides became the refuge of many warring groups of Brythonic-speaking Celts coming in small groups from places between Normandy and the Rhine-mouth in Iron Age A; to be displaced by warriors of ‘La Tène’ culture, who built most of the great hill-forts in their struggle to dominate the lowland zone of Britain; they in turn clashed and merged with Belgic tribes driven from the area now known as Belgium, in about 75 b.c., to conquer the fertile corn-growing areas of Hertfordshire and Essex. The Belgae became known as the Catuvellauni, with their prosperous new capital at Camulodunum (Colchester); their aggression against the older Trinobantes of Essex touched off the invasion of the great Julius Caesar, or so he said.

Thus, when the outraged Trinobantes appealed to Caesar in his Gallic camp, they were the last of the billiard-ball succession of many displaced persons of Britain.