The three major families that we'll be hearing a lot about from here on out (Arthur's family, Gawain's family, and Lancelot's family) all have one thing in common: they have a super-genius who acts like a tutor for them.
So: Merlyn, St. Toirdealbhach, and Guenbors, a.k.a. Uncle Dap.
Uncle Dap, we learn, is a Super Duper Genius of Chivalry and Heraldry. There's really not much this guy doesn't know about these subjects.
Plus, he's the best swordsman in all of France, so we certainly don't blame Lancelot for wanting to learn from the best—even if he hasn't tried the rest.
So, one day while he is hanging out in the Armoury with Uncle D., Lance's mother summons him, because there's a guy there who wants to see him.
His mother's name is Elaine, and heads up: there's going to be a whole lot of Elaines in the story from here on out, because Malory's manuscripts were mixed up.
It's Merlyn, and he randomly tells Lancelot that he'll be the best knight in the world someday. Plus, Guenever sends her love. Oh, but Lancelot hasn't met her yet, that's right. Nothing to see here… just Merlyn getting his timelines mixed up again.
Nimue is the pretty lady with Merlyn. So, it must be almost time for that whole imprisoning in the earth thing that's waiting for him.
Turns out, Arthur meant to send for Lancelot, but the messenger must have gotten lost.
Apparently, Arthur's Round Table has 150 seats available, and he's filled all but twenty-one of those.
When Lance finds out that Gawain has already been made a knight, he's all kinds of jelly.
That's pretty much all Merlyn wants to say, so he and Nimue disappear. Literally.
Lancelot decides he's going to go to King Arthur's court, no matter what his Uncle Dap or mom say. That'll show Arthur for not thinking of him sooner!
So, they set off and get really seasick along the way.