There is really no need, perhaps, for me to tell you that all these stories have been told before. But, though you know it already, I like to say it again, because I can never say often enough how grateful I am to those who told the world first of Arthur, of Guinevere, of Lancelot, and of Gawain; of Galahad, of Percivale, and of Percivale's sister; of the Siege Perilous and of the Holy Grail. If y...