Gaulish society, like all of Celtic society, was rigidly divided into a class system. Similar class systems predominated among the Indians as well with largely the same categories. According to Julius Caesar, the three classes of Gaulish society were the druides, equites, and plebs , all Roman words. The druids were the educated among the Gauls and occupied the highest social position, just as the Brahmin class occupied the highest social position among the Indians. The druids were responsible for cultural and religious knowledge as well as the performance of rituals, just as the Brahmins in India. However obscure these religious functions might be, the druids were regarded as powerful over both society and the world around them. The most powerful tool the druids had was the power of excommunication when a druid excommunicated a member of a tribe, it was tantamount to kicking that person out of the society.
The British did not appear in history until Julius Caesar crosses the English Channel from northern Gaul and began his failed conquest of Britain. The Romans returned in 43 AD and began a systematic conquest of the island until they reached the Pictish tribes in the Scottish highlands. Rome would abandon northern England, however, in 117 AD
The Romans found a disunified group of tribal kingdoms organized around the same logic of warfare as the Gauls. Most of the tribes were new arrivals the bulk of southern Britain had been conquered by the Belgae from northern Gaul. In the process of emigrating to the island, the Celts pushed the native populations north these refugee tribal groups would become the cultural ancestors of the Picts, a mysterious culture that dominated Scotland until the Irish invasions.
Many of the tribes, particularly those in Wales, however, were restive. The Romans were beset by rebellions by some Celtic tribes and depredations by the northen Picts throughout the fourth century, as the Roman empire was strained in every quarter, the Romans slowly lost control of Britain. The official break came in 446 when the Romans in response to a British plea for help against the Picts and the Scots, declared Britain independent.
As in Gaul, the Romans brought Roman urban and military culture; however, other than southern England, Roman institutions and culture were not enormously influential on the British Celts. The Celts in the north and in Wales fiercely resisted Roman culture, and the Romans never even set foot in Ireland. On the whole, the Romans more greatly respected and tolerated Celtic institutions and religions in Britain, so there was considerably less assimilation than in Gaul.
Because of this, when the Romans left Britain, there was a renaissance of Celtic culture. The British, however, had learned a very important concept from the Romans: political unity. The most famous of the Celtic princes was Vortigern, who ruled over eastern Britain. In order to fight against the Pictish invasions, he sent across the channel to get help from the Saxons, a Germanic tribe that had begun emigrating into western Europe in the fifth century. The Saxon mercenaries, however, grew in number as more and more Saxons came to Britain. Whether or not the story of Vortigern is true, Britain fell prey to the same Germanic emigrations and invasions that spread across Gaul, Spain, and Italy. The Saxon emigration began in eastern England until they spread entirely across lowland England. The mountainous areas to the west (Wales) and the north (Scotland), however, remained Celtic, as did Ireland. By the end of the fifth century AD, only Wales, Scotland, and Ireland remained of the great Celtic tribal kingdoms that had dominated the face of Europe.
It was in Ireland that Celtic culture and institutions lasted the longest although Christianity was introduced at an early date, Ireland did not suffer any major invasions or cultural changes until the invasions of the Norwegians and the Danish in the eighth century. The Irish also represent the last great migration of Celtic peoples. In the fourth and fifth centuries, the Irish crossed over into Scotland and systematically invaded that territory until they politically dominated the Picts who lived there. The settling of Scotland in the fifth century was the very last wave of Celtic migration.
For Celtic culture, Ireland is much like Iceland was to the Norse. It was sufficiently removed from mainstream Europe to protect it from invasions and to isolate it from many of the cultural changes which wracked the face of early Europe. It allowed a singular perpetuation of pagan Celtic culture to fuse with Christian and the emerging European culture. This unique synthesis would provide the single most productive line of cultural transmission between Celtic culture and the European culture which grew out of classical and German sources.
Written history in Ireland began in the fifth century when Patrick came to Ireland and introduced literacy. Patrick came to the Celtic tribal kingdom of Tara, which was ruled by Leary, the son of Niall Noígallich. The sons of Niall ruled over two kingdoms in northern Ireland; these rulers formed a dynasty that would be called the Uí Néill; the south of Ireland was largely under the control of Munster. Patrick himself confined all of his activities to northern Ireland and the Uí Néill, particularly around the area of Armagh. Because he introduced the Irish to Christianity, European culture, and writing, he became the patron saint of Ireland.