The most important culture inhabiting
Britain was that of the Celts, a culture transplanted from Gaul.
In the first century BC, people began crossing the channel and
settling the countryside. The Belgae settled in the southwest,
while maintaining ties with their homeland, Galia Belgica, but
the Celtic tradition predominated.
Caesar named six tribes, including the Trinovantes and Cenimagni (Iceni?). Four were left unnamed in Kent, and there is an implication of a nameless eleventh, possibly the Catuvellauni, ruled by Cassivellaunus, who led the British opposition. Other tribes who played a part during the time between Caesar and Claudius and the time immediately after were the Brigantes, Corieltavi, Cornovii, Dumnonii, Atrebates and Dobunni, located in present-day England, and the Silures and Ordovices in Wales. The Catuvellauni gradually conquered south-east England. Also, the four tribes of Kent eventually came together and formed the Cantiaci tribe.
After the invasion, the Britons tended to stick to their Celtic traditions, and the Romans let them. The Romans believed that the Celtic custom could blend with the Roman traditions. Because of this the Celts were able to worship their own gods, and were encouraged to keep their tribal system running (under Roman supervision, of course).
Even though after the Romans left men spoke of Rome and wrote in Latin on the tombstones, the Celtic spirit was alive and flourishing.