So at the end of the last chapter Malory explains to us that Arthur ends up ruling all of Great Britain, Wales and Scotland and all, but it turns out that was just a spoiler for future events, because the next few chapters are all about the tale of Arthur making war upon the kings of the parts of Great Britain that he’s not king of. We’re at Pentecost, Arthur has been crowned, and the folks who live south of the river Trent pretty much all accept him as king.
He takes a trip to Wales, just after his coronation, and throws a big feast at Caerleon there, Caerleon being the best place available. I’m honestly unsure whether Malory means this trip to have happened immediately following his coronation in London, or if he spends a full year establishing himself as King of Much of England and then at next year’s Pentecost travels to Caerleon for a second coronation party. It doesn’t really matter for purposes of the story — if it was a year, it was a year at the end of which there was still a lot of Great Britain that he didn’t rule. Plus there was the earlier assertion that he spent two years conquering everything, so is this a celebration of that? Best not to worry about it. It’s very early in Arthur’s reign, not everyone accepts him. That’s the context, here.
Anyway, at Caerleon he throws a big feast and invites all the other kings in the area, which includes his three brothers-in-law from Chapter II (Lot of Orkney who married Margawse, Nentres of Garlot who married Elaine, and Uriens of Gore who married Morgan le Fay once she graduated from necromancy school). Other kings in attendance were the King of Scotland, whom Malory doesn’t name, the King of Carados, and a king known to us only by the epithet “the King with the Hundred Knights.” They all bring along hundreds of knights with them, so it’s a gigantic party, which thrills Arthur because this is his first major kingly act, this party, and look at the turnout!
However Arthur’s glee soon turns to disappointment and despondency, because this conversation keeps happening:
ARTHUR’S MESSENGER: Hey, King Lot/King Nentres/King Uriens/King Scotland/King Carados/King Mister 100!
MESSENGER: Arthur wanted you to have this gift basket and thank you for coming to his celebratory Arthur-is-King-of-Everything-Outranking-All-Other-Kings party.
KING: Get bent!
(KING throws gift basket in MESSENGER’s face.)
It turns out that if you’re the king of, say, Carados, and you get word that some punk teenager who isn’t even the son of anyone important (you’ve never heard of his dad Ector and besides they say he was adopted) has declared himself Super-Mega-Ultra King, you’re disinclined to cheerfully swear fealty to him, and when you show up at his party with a few hundred heavily armed men, it’s not really a social call.
Malory turns a nice phrase here: the other kings “sent him word they would none of his gifts, but that they were come to give him gifts with hard swords between the neck and the shoulders.” Well, it’s a nice phrase compared to Malory’s usual output.
Reluctantly Arthur makes ready for the coming rumble. He’d rather not fight, so he holes up in a tower with a few hundred men of his own and waits for the other kings to leave. A couple weeks of siege go by, nothing getting resolved, neither side giving up; Arthur has all his party food in the tower and the kings are motivated to give the little twerp what-for.
Fortunately Merlin shows up to fix the situation. All the kings outside the tower know Merlin, of course, everyone knows Merlin, and they’re all, “how’s it going, Merle, you’ve come to cheer us on?”
And Merlin is like, “no, no, Arthur is the rightful king, you guys are on the wrong side of this issue.”
The kings are all, “wha?” And Merlin goes, “listen, he’s actually Igraine’s and Uther’s son, remember Uther? Kind of a dick but still the king of everything.”
One of the kings does some quick math, Malory asserts, and deduces that if Uther fathered Arthur on Igraine, it must have been while she was married to Gorlas, otherwise the timing doesn’t work. Therefore Arthur is a bastard, therefore not the rightful king. I would be unconvinced by that, given the tight timing of Arthur’s conception, Gorlas’s death, and Uther’s marriage to Igraine, but it goes over well with the assembled kings. You might even say they demand to see the birth certificate.
“I anticipated your objection,” says Merlin, and produces a long-form Hawaiian certificate and a chart and timetable and deck of Powerpoint slides showing that Gorlas had been dead for three hours when Uther and Igraine slept together and that less than two weeks later Uther and Igraine wed, so, Arthur’s definitely not a bastard.
“Well, shoot,” say the assembled kings.
“He’s definitely king, you guys,” says Merlin. “And he’ll be king for a long time, King of All England, which includes Wales and Scotland and Ireland, the whole schmear. Unless someone murders him, I mean. If he dies, say putting down a civil war, then he won’t be king long. But for right now he’s totally the rightful king.”
King Lot, at this point, has gotten sick and tired of Merlin and his damnable Powerpoint slides, and calls him a “witch” and a “tiresome jack-ass,” and refuses to accept what Merlin’s saying. But he’s in the minority; the other kings by and large are at least willing to hear Arthur out.