A/N: This is my first time writing for the Merlin fandom, I wasn't sure where to stick this but as the two main characters are Arthur and Gwen I figured this was as good a place as any to put it. This is my version of the inevitable Guinevere/Lancelot betrayal in the original Arthurian legends. This story contains Arwen, Gwencelot and sort of Methur but not really. Due to her personality on the TV Show if Gwen was to have the affair with Lancelot than there would need to be real reasons behind it (ignoring the enchanted by Morgana episode recently in Season 4). I wanted to write a piece in which no one is completely at fault and no one is completely innocent.

Warnings: If you're a hardcore Arthur and Gwen shipper and hate the idea of them with anyone else then this probably isn't the fiction for you.

Reasons For Betrayal

Guinevere Pendragon continued to stare blankly out of the window as the door to the tower opened and her husband entered the room locking the door behind him. She ignored his presence and remained seated in the small chair, her fingers fiddling with her dress and a needle, becoming reacquainted with the feeling of stitching up her own clothes again in a way she had not done for many years. The sun was hanging lazily in the sky, having only risen a couple of hours ago. The early bustle of the people of Camelot echoed around the grounds. She watched as they darted back and forth across the streets. How she longed to be one of them again, happy and free no longer entrapped in this life of royalty and duty. She wished she was free to follow her heart.

The King stood before her; she could see him out of the corner of her eye, his heated glare boring into the side of her skull. However, she refused to bow down to him, to acknowledge him...not after he'd locked her away in this wretched tower.

'I just want to understand why,' Arthur said, his voice biting like ice on the skin, 'How could you do this to us...again, and with him of all people!' His voice rose to a yell and he picked up the empty side table and threw it across the room.

She flinched as the wood smashed against the stone of the walls falling to the ground in splinters. Pulling her eyes away from the window she finally looked upon her husband's face. He was breathing heavily, his cheeks were flushed red from anger and his eyes were bloodshot and puffy.

'Anything I have done, any act I have committed is your fault, and yours alone,' she replied her voice devoid of bitterness and anger; she looked up at him with only deep resignation and pity.

'My fault! How could you possibly hold me responsible for your affair? I have done everything for you Gwen, I married you, and I made you my Queen. What else could I have possibly done to secure your happiness and loyalty?' he yelled stalking forward and placing a hand on either side of the chair loomed into her face.

She refused to look away, staring calmly back at him, 'You should have left me alone, and you should have married some other woman who did not love as I did.'

He blinked rapidly moving his head away from her. His mouth opened and closed a few times before asking, 'Are you saying you made a mistake in marrying me?' Arthur watched her cautiously as though he feared the answer.

'I am saying that had I known then what I do now. Had I known what a lie my life would become forced to forever live in the shadow of another then I never would have agreed to marry you,' her voice was soft and filled with a deep rooted pain.

'You knew who I was; you knew that I was a Prince, that I would someday become King. You knew that Camelot would have to come first, I never once lied to you about that.'

She choked out a hollow laugh at him and Arthur backed off disgusted and began to pace in front of her, running a finger through his hair, blonde with flecks of grey.

'I am not talking about your status as King or Camelot, I always knew that when it came down to it I would be forced to take second place to an entire Kingdom. It was something that I was willing to accept. After all, your love for your people, for Camelot and your devotion to them was part of what made you...well you. It was one of the things I loved the most about you. But the truth is I don't even come second in your heart, do I?'

'I...I don't...' he muttered, halting in his pacing to stare at her incredulously.

'You don't even realise do you? You don't even realise...and why would you it's become so natural to you, its destiny,' she said smiling pityingly at him.

She watched as Arthur blinked that word having so much meaning in the man's life, especially when it involved...

'Merlin? You think Merlin and I are...?' He stared over at her as though fearful for her sanity, 'you cannot be serious?'

'I wish it were a joke. Do you know when Princess Mithian came to pay her respects to me after our wedding she said something curious? She asked how it felt to be married to Arthur and Merlin,' she looked away from her husband back out of the window, 'at first I thought it was just a little joke at how the two of you were always together. However, looking back I realise that she was being serious. I wasn't just married to Arthur Pendragon, Merlin was always there, he never left and what's more you wanted him to be there. At first I thought nothing of it, at the time he was still your man-servant and it was to be expected that he be around to attend to your every whim. Yet when things changed, when you made him your advisor instead he was still there. Do you know I can count the amount of times it has just been the two of us in the past year on one hand,' she whispered turning back to look at him

Arthur looked away from her looking guilt stricken, running his hands through his hair in frustration.

'I couldn't even begin to count how often you are alone with Merlin. You spend most evenings in one another's chambers.'

Arthur opened his mouth to speak but she raised her hand to stop him, 'Do not think I assume you are sleeping with him. I know there's nothing sexual there between you. No, what you feel for him goes so far beyond that, is so much more terrifying than that. It must hurt so much to be in love with someone, to know that no matter how much you want them, you don't want them. Does it make you wish you were attracted to men instead? That one of you had been born a woman?'

'Don't!' Arthur yelled, his voice cracking slightly.

She ignored his yells; this was something he needed to understand. She needed him to see just how much pain he had caused her after seven years of living in this twisted excuse of a relationship.

'You know I felt special when you went against the protests of your council, when you ignored the social boundaries to marry me. For a moment I felt satisfied knowing that you were willing to bend the rules because you loved me. Then you bent the same rules for him as well, you made him your Advisor despite his peasant status, and I watched you shatter almost every rule your father instated on this land.'

'The laws were wrong, people with magic did not deserve to be persecuted, and they did not deserve to be killed for their beliefs!' he yelled standing defensively.

'But that is not why you did it!' she yelled back.

He stumbled backwards slightly in shock.

'You discovered who he truly was, you finally discovered Merlin was a Warlock and you banished him because you couldn't handle the betrayal of being lied to all those years! I watched how much it hurt you, how it almost killed you. You weren't sleeping, you were barely eating, and you didn't care for your duties as King. It was like you were missing half of yourself. I remember how you pushed me away, yelled at me to leave you alone. You locked yourself away for almost a month before you went after him.'

'He's my best friend Gwen, even if I couldn't admit it at the time, he was my best friend then too. My only true friend you know that.'

She shook her head, tears springing into her eyes again, 'we both betrayed you, you had us both banished, but you went after him,' she said softly staring at him as though daring him to deny it, 'you never came after me. It was only running into me in Elador that we were ever reunited.'

Finally Arthur looking tired sank into the chair sat opposite hers; dejectedly he placed his head in his hands.

'And when you finally brought him home, I watched you tear down ever anti magic rule one by one. You turned the country on its head, and almost caused wars with allied countries...all for him all, to make him happy, so you could keep him by your side. And he would do anything for you, would hand you the sun if you asked if of him. He'll even kill another to keep you safe. You've both fulfilled those ancient prophecies; you've built Albion from the ground up and all with Merlin at your side as it was always meant to be.'

They both sat in silence, Arthur with his head resting in his hands, his palms pressed into his eyes and Gwen returning to stare out the window.

'I do love you Gwen,' Arthur said finally his voice cracking. He stared up at her with watery eyes and her heart clenched painfully.

'I know you do, just not the way I wish, not the way you love him. It's not enough Arthur, I don't deserve to be living as second best to another,' she said, her voice resounding with conviction.

'And Lancelot?'

The calm expression and dulled demeanour as Arthur expressed those words felt like a release of all her tension. He was no longer fighting for her, he had given up. That he could say Lancelot's name without anger or jealously confirmed everything, and made what she had yet to do that much easier.

'He loves me, he truly loves me. He always has and would do anything for me I will always be first in his eyes. I've always loved him, even though I once loved you more, he's never completely left my heart. Things were never supposed to get this messed up. We were never meant too... I was just so lonely, so unhappy and he was there,' she said wistfully.

'How long?' he asked, looking as though he was dreading the answer.

'Four years,' she said solemnly watching Arthur's head jerk back as though it had been slapped.

'Four years,' he repeated dismally, 'Over half our married life has been a sham and I never even noticed. I'm so sorry Guinevere.'

She reached forwards and placed a hand on his knee over his own larger hand, 'It's okay Arthur, I've known for years now. I would never have tried to come between the pair of you; I care about you both too much. Besides he completes you, without him you aren't Arthur and without you he is not Merlin.'

Arthur nodded moving towards the door, pulling the keys off of his belt he unlocked the tower door again, 'you shall have your horses, and as many supplies as you need. Take Lancelot; Guinevere and leave Camelot. I hope you finally find the happiness I could never give you,' he said sadly staring down at the floor, his eyes blurring with tears again as he held the door open for her.

She stood in front of him and leaning on her tiptoes kissed him softly on the cheek, 'Thank you Arthur. You should head back to your chambers; he's probably worried sick about you. You know what he's like when he's worried.'

'He's such a girl,' he said chuckling fondly.

Gwen smiled, 'May I ask you something before I leave?'

'Anything Guinevere.'

'Does Camelot really come first?'

'If Camelot was no more, I could still go on,' he replied simply, his face turning red from embarrassment.

'Take care of him Arthur, and look after yourself,' she said finally before stepping out of her tower and walking down the stairs, leaving her old life behind.

'My lady, are you ready to leave?' Lancelot asked as the last of the horses were loaded up. His face was bowed guiltily to the floor as though he blamed himself for her banishment.

'Yes, I am,' she said before stroking his face lovingly. He looked up at her and she smiled at him. He stared into her eyes as though attempting to detect pain or sorrow and when he could see neither he relaxed.

A cough echoed to her left from her brother and as she looked at him apologetically he helped her onto her horse, before mounting his own. Despite his loyalty to Arthur; Gwen was his sister and his only remaining family and had chosen to follow her and Lancelot on their journey. In her years living in Camelot she had gone from Blacksmiths daughter and servant to becoming Queen and now she was leaving as an adulteress. She could not bring herself to care though; she would not be returning to Camelot, her life felt like it was just beginning. As Lancelot and Elyan began to move she glanced up at the familiar window to Arthur's chambers, and was able to see Arthur and Merlin stood there holding one another Arthur's face buried in the other man's neck. Merlin gripped onto him as though they would both fall should he ever let go, which Gwen mused they probably would.

She made her horse follow her brothers and her soul mate's both of them riding off away from the castle and on to embrace their destinies.

A/N: Reviews are welcome :)