<P> Diodorus Siculus and Pliny both suggest trade between the rebel Celtic tribes of Armorica and Iron Age Britain flourished . In 55 BC Julius Caesar invaded, claiming that the Britons had aided the Veneti against him the previous year . He was more successful in 54 BC, but Britain was not fully established as part of the Roman Empire until completion of the invasion by Aulus Plautius in 43 AD . A brisk and regular trade began between ports in Roman Gaul and those in Britain . This traffic continued until the end of Roman rule in Britain in 410 AD, after which the early Anglo - Saxons left less clear historical records . </P> <P> In the power vacuum left by the retreating Romans, the Germanic Angles, Saxons, and Jutes began the next great migration across the North Sea . Having already been used as mercenaries in Britain by the Romans, many people from these tribes crossed during the Migration Period, conquering and perhaps displacing the native Celtic populations . </P> <P> The attack on Lindisfarne in 793 is generally considered the beginning of the Viking Age . For the next 250 years the Scandinavian raiders of Norway, Sweden, and Denmark dominated the North Sea, raiding monasteries, homes, and towns along the coast and along the rivers that ran inland . According to the Anglo - Saxon Chronicle they began to settle in Britain in 851 . They continued to settle in the British Isles and the continent until around 1050 . </P> <P> The fiefdom of Normandy was created for the Viking leader Rollo (also known as Robert of Normandy). Rollo had besieged Paris but in 911 entered vassalage to the king of the West Franks Charles the Simple through the Treaty of St. - Claire - sur - Epte . In exchange for his homage and fealty, Rollo legally gained the territory he and his Viking allies had previously conquered . The name "Normandy" reflects Rollo's Viking (i.e. "Northman") origins . </P>

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