Mordred was King Arthur's villainous illigitimate son by his half-sister Morgause. We'll let him explain why he chose that and not something like Percival or Galahad

Avalon was the fabled isle to which Arthur was taken when he was mortally wounded -- there to sleep through the ages until Britain needed him once again.

Tolkien, author of The Lord of the Rings, was well aware of this most British mythology. The ship that travels from the Grey Havens to the far west at the end of the book is a direct parallel with Arthur's journey to Avalon.

I's a long time since I read any of this. Maybe I should pick it up again.