The children of May Day

Before he is married, and without knowing who she is, Arthur sleeps with the wife of King Lot of Orkney, who has come to his court as a spy. She is Morgause, his half-sister on his mother's side. Neither of them knows.

Merlin tells him afterwards, and does not soften it: Arthur has begotten a child who will destroy him and all the knights of his realm.

What Arthur does next is the worst thing he ever does, and Malory reports it in a single flat chapter. He has it proclaimed that all the lords in the country must send him every child born on May Day, gentleborn or not. They are sent, many of them, and put together into a ship, and the ship is put out to sea.

The ship is driven onto rocks and breaks up. Most of the children drown. One is found by a good man and fostered until he is fourteen, and then brought to court.

That child is Mordred.

Malory adds one more sentence, which is the most damning thing in the chapter: many lords and barons of the realm were angry that their children were lost, and many put the wite on Merlin more than on Arthur — many blamed Merlin rather than Arthur. He does not say whether they were right.

This is the story's clearest statement of what foreknowledge is worth. Arthur is given accurate information about the future. He acts on it decisively, at enormous moral cost, and the action he takes is the mechanism by which the prophecy comes true: had he done nothing, Mordred would have grown up in Orkney as one nephew among four.