We cut back to England and flash back to just after Arthur and Gawaine sail away with their sixty thousand troops.  Mordred, Guenever, and all the other survivors of Book XX stand on the dock and watch them go.

“Well, they’re dead,” says Mordred.  “I mean, come on, they went off to make war against Launcelot.  We’re all thinking it.  They’re dead.”

The various assembled knights exchange glances and mutter noncommittally.

“Yeah, they’re dead,” Mordred says.  “That guy who said they were dead, he was right.  I’m king now.  Everybody?  I’m king now!”

Guenever scowls, because this is another situation where her whole purpose is to be a chit in one of Arthur’s damn games.  “So you’re king now.”

“Yeah, yeah, I’m definitely the king now,” says Mordred.  “King Mordred.  That sounds okay, right?  I don’t need to change my name to Arthur Junior?”

“I don’t think that would be wise.”  Guenever’s eyes narrow.  “I’m still the queen, though, yes?”

“Yeah, of course.  You’re queen, I’m king… hey!”  Mordred snaps his fingers, realizing something.  “That means we’re married!”

Guenever scoffs.  “We are not married!  I married Arthur!  If I was going to marry someone else, you’re way down on that list.”

“But I’m king!  We’re married if I say we’re married!  And I say we’re married!”

“Nope.”

Mordred sulks for a moment, then has an idea.  “Then we’ll get married!”

“What?”

“Wedding!  A compulsory wedding!”  Mordred loves this idea.  “You, my father’s wife, my uncle’s wife!  You and me, getting married!”

“Um.”

“Yes!  Mandatory wedding, everybody!”  He turns to the collected knights.  “Three cheers for me!”

The knights cheer.  It’s kind of ragged at first, but then things pick up, because knights love cheering.  “Hooray!  Hooray!  Hooray!”

“Hooray,” Guenever says weakly.  She can see where this is going.  “Mordred, darling boy…”

“Call me ‘Mordy Baby!’”

“Mordy Baby,” Guenever says because she knows to pick her battles.  “We’re going to need tablecloths, and candles, and roast suckling pigs, and maybe the Decemberists to play the reception… all kinds of supplies.  A lot of stuff.  A lot, a lot, you know?”

“Uh huh?”  Mordred is much more concerned with waving at the crowd of knights than he is listening to Guenever.  “Sure, sure.”

“So I’m going to go down to London, okay, and make some arrangements.  Get a dress, hire some caterers, throw together a web site, record a Kickstarter video, you know.  I’ll meet you in Camelot, ‘kay?”

“Sure, sure.”

So Guenever sneaks off from the dock and rides with some of her ladies to London!  Once there she buys a big pile of food and wine, like you would for a wedding reception, but instead of the Decemberists she hires mercenary guards, and instead of recording a Kickstarter video she locks herself in the Tower of London.

“I’m not coming out!” she shouts down to the crowd.  “I live here now!  Arthur’s dead, Launcelot’s gone, there’s nothing for me out there!”

Eventually Mordred hears about this.  He goes to London to try to talk her into coming out, but it’s a real nonstarter, even after Mordred tries starting fires and firing cannons and shouting insults up at her, which are all his best ideas.  Mordred’s down at the bottom of the Tower of London, pacing around, when the Archbishop of Canterbury stops by.

“So, Sir Mordred,” the Archbishop begins.

“King Mordred,” he says in correction.

“Right, right.  About that.  Listen, you know that according to the current Church doctrine, marrying your father/uncle’s wife is incest?”

“Incest didn’t hurt my uncle-father any.”

“Mmm.  Well, regardless, the Church is pretty clear on that.  It’s really pretty skeevy.”

“Shut up,” says Mordred. “I’m sick and tired of your attitude, guy who I just met for the first time!”

“Also I’ve been in communication with the clergy in Benwick, and they say Arthur isn’t dead…”

“I said shut up!”  Mordred pulls his sword.  “You want I should slice your head off?  Because I totally will!”

The Archbishop steps back, out of melee range, and flees.  He doesn’t return to Canterbury; instead he escapes into the wilderness and becomes a hermit out in the middle of nowhere.