Native Tribes of Britain
The British Isles
This map shows the approximate location of the major tribes who lived in Britain at the time of the Roman Conquest of Britain in the First Century AD. The sole source for the existence and location of these tribes are Roman writers who visited Britain.
One of the best observers of the tribes of Celtic Britain was Tacitus who wrote on historical events in Britain. Another was a Roman geographer called Ptolemy who wrote a description of Britain, listing the names of the many British tribes.
http://www.bbc.co.uk/history/ancient/british_prehistory/iron_01.shtml
