Who does Leodogran summon to prove Arthur's birth in Idylls of the King?

Leodogran first summons three of Arthur's knights to the court. They swear that he is truly Uther's son, though he was raised by Anton, a mere knight. He then summons Bellicent, the daughter of King Lot who knew Arthur when she was a child. She relates a tale told to her by Bleys, Merlin's master, according to which Arthur was miraculously borne to Earth on the sea.