The Celts who had first arrived in Wales in the 6th and 7th centuries B. C. were defeated by the Romans in 43 A. D. The Romans also killed large numbers of Druids, the Celtic religious leaders. These Druids could not read or write, but they memorized all the things about the laws, history, medicine necessary for the Celts. The Saxons pushed the Welsh further and further towards the west until, in the 8th century, a Saxon king called Offa built a long ditch to keep them out of England. Then came the Normans who built huge castles to protect themselves from attacksfrom the west. The Welsh fought for many years to win back their freedom. The Welsh king, Llywelyn the Great, tried to unite his people against the English, but his grandson, Llywelyn the Last, was finally defeated in 1282. The English built great castles in Harlech and Caernarfon, and in 1301 Edward I of England made his eldest son prince of Wales. This tradition has been kept until the present day and in 1969 such a ceremony took place again. The Queen made her eldest son, Charles, Prince of Wales at Caernarfon castle.