Disclaimer: I own nothing you recognise.

AN: *Arthurian legend spoiler* You all know that in the King Arthur legend, Guinevere ends up running off with Lancelot, right? And judging from the Lancelot-Gwen-Arthur thing they've got going on in the show, I'm gonna guess that they aren't planning on deviating from that part of the legend. And I wondered how Gwaine would take it, if he found them out.

SPOILERS for the Arthurian legend, and for Season 3 of Merlin.

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The Queen's Betrayal

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"Lady Guinevere," he calls from behind her, and as she recognises his voice she turns to greet him with a smile.

"Sir Gwaine," she says, thrilled to see him safely returned. "I'm so glad you're home safely. I trust your mission went well?"

"Very," he says, and it's the first that she notices that his face is unsmiling and his dark eyes are serious. "We caught the bandits that had been plaguing the villages. They're in the dungeons now."

"That's... very good to hear," she says, a little hesitantly, trying to work out why he's not grinning his usual easy grin and throwing out his classic one-line charmers. "Is there something I can do for you? You seem... troubled."

His seriousness is disconcerting, and she's starting to get a little worried.

"Actually yes, Your Majesty. I was wondering if I might have a word with you. In private."

She's more than a little concerned now, because he never calls her that unless he's joking around (and he's very clearly not joking right now) and it's very unlike Gwaine to be serious about anything, so whatever it is that's got him acting like this has got to be bad.

"Of course," she agrees instantly, turning and starting down the hallway. "Arthur is out with Merlin all day, seeing to the drought problems some of the western flung villages have been having – our chambers will be free."

He says nothing as he follows her down the hall, and his silence is loud as their footsteps echo and bounce off the stone walls.

She enters the Royal Chambers first and he follows, shutting the door behind him and leaning his forehead against it for a second, taking a moment to gather his strength.

When he turns to face her, she gasps a little at his expression of utter devastation.

"Gwaine!" she cries, completely baffled and far more than a little concerned. "Gwaine – what is it?"

"How could you do this?" he asks her, and a part of her brain goes still and quiet even as the other half of her says that he couldn't possibly know – that couldn't possibly be what he's asking about.

"Do what?" she asks, pushing her secret thoughts aside, beyond concerned about the knight in front of her. "Gwaine – what are you talking about?"

"I think you know Guinevere," he says, his voice sounding broken and betrayed and shattered.

The seriousness is completely out of character for him, and Gwen's heart flutters nervously as she takes in his devastated expression.

He knows, she realises, and she feels her stomach plummet in horror.

"I saw you both," Gwaine goes on, and if there was any doubt as to what he's talking about he's rapidly clearing it up. "Last night, when I returned with the soldiers. I dismissed the rest of the men and went to report to Arthur. And on my way back I saw you both, heading out into the woods. And I followed you."

There's a silence as Gwen stares at him, horrified at what she knows he saw.

"Y... You followed me?" she stammers, and she knows that the little bit of anger that's slipped into her tone is unwarranted, but she can't help it.

He picks up on the tone, and his face flashes in anger.

"Of course I did," he snaps, glaring at her. "I see my Queen sneaking off into the woods with just one Knight with her to protect her – of course I was a little concerned. I thought you were... I don't know, sneaking off on some kind of mission or something. I expected almost anything except – "

He cuts himself off suddenly and spins around, running his hands through his hair and swallowing his anger forcibly.

"Aren't you going to deny it?" he asks once he's calmed himself a little, his voice quivering with barely suppressed emotion.

Guinevere blinks rapidly and looks at the ground, trying to force back her sudden tears. She hardly deserves to cry about this, after all.

"What's the point in denying what you saw?" she whispers, forcing the words past the lump in her throat.

She glances up, and Gwaine is looking at her again, pain and anguish clear on his face.

"How could you do this to him?" he asks brokenly, and it's clear who he's talking about.

"I-I," Gwen fumbles, trying to speak, but he cuts her off, suddenly angry again.

"How long?" he demands, taking a half step towards her that automatically has her hurriedly retreating.

"S-since the tournament," she whispers, not quite able to make her voice come out any louder. "L-Lancelot was injured, if you remember, and I-I was helping out with his care and..."

She glances up at Gwaine again and he's shaking his head, not looking at her, his eyes full of disgust and disbelief.

"Does Merlin know?" he asks, his face hard and his jaw clenched.

"No," she whispers, tears welling in her eyes again. "I couldn't tell him. You know how close he and Arthur are – he would feel honour bound to tell him, and I can't put him in that position."

"Is that because you don't want to put him in that position, or because you don't want Arthur to know?" Gwaine snaps coldly.

"B-both," Gwen says after a moment, her voice quivering. "Please. Don't... don't tell him."

Gwaine stares at her, incredulous, and she knows she had no right to ask that of him.

He is (was?) her friend, yes, but his allegiance has never been to her. Merlin was the first to secure his loyalty, followed by the then-Prince, and he will never betray them (unlike she has).

"You don't think that I have the same duty Merlin does?" he demands. "That I am not honour bound to tell him what his own wife is doing behind his back? He's my King and friend, Guinevere! What am I supposed to tell him? How could you do this to us? To him! And Lancelot...! I don't even know where to start with him. Of the Knights, he's the closest to Arthur. I just... I don't understand how you two could –"

He cut himself off again, apparently too distraught to continue, turning away from her again and gripping his hair as though he intends to rip it out by the roots.

She watches him silently, still valiantly fighting the tears she knows she has no right to cry. She brought this upon herself after all.

"Can you at least tell me why?" Gwaine asks eventually, his voice cracking over the whispered words, and Gwen feels the lump in her throat swell even further.

"I didn't mean for this to happen," she whispers brokenly, and she feels her tears spill over. "I never wanted to hurt Arthur."

Gwaine spins to face her again, fury warring with betrayal warring with incredulity for the most dominant expression on his face. There are tears glinting in his eyes – unshed, for the moment, but a little piece of Gwen breaks at the sight.

"You didn't mean to hurt him?" he repeats, as though he can't understand the words. And in a way, he can't. "What did you think would happen? Guinevere – Arthur adores you! He loves you more than he loves Camelot – how could you think this would end in any other way than him getting hurt? You're having an affair with his most trusted knight!"

It's the first time the words have been spoken aloud, and Gwen feels like she's been slapped in the face and a sob bursts free of her chest before she can remind herself that she doesn't have the right to cry over this.

"I didn't... I – I never intended for it to happen! Gwaine, please – I never set out to hurt him. I can't... I can't explain – Lancelot and I... he... Gwaine, I've loved him for as long as I've loved Arthur! Longer, even. And... I know it's wrong and I know I shouldn't, but I love both of them! Can't I love both of them?"

There is nothing but cold anger in the panes of Gwaine's face.

"Not when you chose one," he says, fury and betrayal glinting in his eyes. "Not when you chose Arthur."

She sobs again – because she knows he's right and yet how is she supposed to choose? – and he cuts her off before she can attempt to explain herself again.

"You've ruined us Guinevere," he says, and his voice is all broken and devastated again. "How do you expect us to come back from something like this? For Arthur to come back from this? We expect enemies from the outside, not from within our own walls."

She knows he's right, even though it would hurt less to brand her own arm than it does to hear his words.

"This has to end, Guinevere," he says, and she's never seen him so serious about anything in all the time she's known him. "I can't allow this to continue. You've got to end it. Immediately."

"But," she stammers, even though she's known from the moment Gwaine revealed that he knew that he would say this. "But Lancelot... he'll be devastated. I can't... how can I do that to him?"

"The same way you did it to Arthur," he half snarls, his fury swift and sudden at her words. "You need to choose, Your Majesty. You can't have both of them. Choose, and if we're lucky we'll just lose one of them. But if you keep this up, there's no doubt that we'll lose them both."

"H-how am I supposed to choose?" she asks, her voice hitching in a sob half way through.

"You've done it before," he says, and his voice holds no mercy or pity, only anger and contempt and betrayal. "Do it again. And there'll be no changing your mind this time."

She cringes.

"W-what would you have me do?

Gwaine shakes his head at her, his jaw tight.

"I cannot tell you what to do. You have brought this upon yourself. No one can make this decision for you. You'll only regret it later, and then we'll be right back here again. And I will not allow that to happen."

She nods, hearing the logic in his voice. She has to decide. She has to decide whose heart she will break, and she will have to live with the consequences of that action.

Her face is tearstained and botchy, her eyes red and her hands shaking. She's never looked less like a Queen in her life. Never felt like less of one either.

Abruptly, he walks to the door and wrenches it open, and it's apparent that he's done.

Nearly, at least.

"I'm serious Guinevere," he states, and those words are hardly necessary. "End it. I'll not allow you to hurt Arthur any more than you already have. If you do not end it, I will."

She nods again, sobbing a little even as she tries to reign in her emotions.

"Your Majesty," he says by way of farewell, with none of the familiar and friendly tone he once had, but all of the anger and betrayal and coolness of someone you have wronged to badly for it to ever be right again.

The words are said with a hint of irony to them, as though Gwaine feels like the title is one she no longer deserves.

She can't help but agree.

Her last sight of Gwaine is of his devastated and furious and betrayed eyes, as he slips out the door and closes it firmly behind him.

There is silence in the Royal Chambers for a long moment as Guinevere stares at the closed doors. And then she sinks down to the floor and lets loose all the emotions she has no right to feel.

Arthur finds her there, hours later, sitting balled up in the corner of their chambers.

When he asks her what's wrong – his concern and love and worry shining bright enough in his eyes that she has to look away – she can't think of anything to tell him but the truth.

She can't bring herself to look at him, and maybe that's a good thing, because if she had, his shocked and heartbroken face would have haunted her dreams for the rest of her days.

She asks him what they'll do now.

He tells her to get out.

He means "Get out of this room; I need time to think."

Whether she understands his meaning or whether she does not doesn't matter.

She makes her choice.

The Lady Guinevere departs Camelot for good with Lancelot that night, leaving behind a broken King and a shattered country.

Gwaine watches the two of them leave from the window in his chambers.

Neither of them look back once.

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End

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AN: Wow. How's that for angst.

Now, I love Guinevere – I do – and I love Lancelot. But I don't understand how they could to this to Arthur, who has never shown either of them anything but love and respect.

In seasons one and two I ADORED Lancelot, and in 2x04 I spent a great deal of time discussing with my sister the fact that I completely understood the division Gwen felt, because I wouldn't know who to pick either. But then she picked Arthur and, I'm sorry, but she's made her choice now, and that's that.

And then Lancelot came back in at the end of the third season and I felt a gut-awful tragic angst for him, because he loved Guinevere and she's picked Arthur, but somewhere along the way it morphed into an anger over what I know he'll do to Arthur in the end, and suddenly I liked him a whole lot less.

Hence, where before it was Gwaine and Lancelot vying for the position of Bundi's-Favourite-Knight, now Gwaine is the clear and unchallenged winner. All because of something that Lancelot has not actually done yet (in the show). A little unfair, maybe, but I can't bring myself to forgive either him or her for their future actions.

Please do me the honour of reviewing.

Bundi.