For starters history is who wrote it. The reason that King Arthur is a ‘myth’ is because the Christians wrote him out of history. They could not allow the greatest king in England’s history to be a Druid. What ‘documentation’ if you will, or what stories are handed down all tells that Arthur was a Druid; he was the last Druid king.
They Christians have they’re fingerprints all over ‘The Legend of King Arthur’. Morgana is written as an evil seductress, Guenivere as a virtuous victim, Lancelot as a knight in shining armor, and Arthur as the product of sin and a bastard. His rise to the throne was of witchcraft and he had alliances with witches and wizards. He was cursed with a barren wife and a child of incest conceived through magic from his sister Morgana. His kingdom fell into ruin after the birth of his son Mordrid.
Then there was the quest for the Holy Grail. We all know that the Grail, a cup, is a symbol of Christ. To drink from the Grail was to accept Jesus as your savior. Legend has it that after years of his knights searching for it The Green Knight hands it to his King who drinks and the land is reborn, his army unites and they go to one last battle against Mordrid. They kill each other in battle thus ending the bloodline.
The symbolism of Arthur drinking from the Grail is to say that he died a Christian and that Christianity saved England from Paganism