Author's Note: It's probably never really come across in my writing (as my favourite pairing, Addison and Alex, no way relates to it) but for me, the absolute best character dynamic in Grey's Anatomy lies between Derek, Mark and Addison. There's just so much to explore there, and I would write it more often if I felt I could do it justice. There are so many layers going on, and this is my idea for just one of them. The idea, obscurely, actually came a while ago, watching an old CSI New York repeat, and I'm a bit blocked on the next chapter of We die on the march so I thought I'd have a go at writing this one out. The rating for this piece is T, but there is a bit of language that some may consider a little strong, so please be warned. Consider this set at an indeterminate point in early Season 3, fairly recently post-divorce. And of course, it goes without saying that I would love to hear your thoughts.

Disclaimer: Let's make one thing clear, if I was anything to do with Grey's whatsoever, it would not have been Addison packed off to a sun soaked Californian spin off. And the quote from Winston Churchill.

'History is written by the victors' – Winston Churchill

At some point, several hours and a dozen drinks ago, drowning his sorrows at the Emerald City Bar had probably seemed like a really good idea. The alcohol would gradually erode away the sharpest edges of his despair until it went from a sharp pain to a dull ache, and with any luck, some pretty girl would walk into the bar and he would turn on the charm and he'd manage to erase even the ache, for the night at least.

Now though, he wasn't so sure. There wasn't a prospect that had walked in all evening, and his liver was beginning to curl up at the amount of whiskey it was being asked to deal with. Worse of all, being drunk had done absolutely nothing to improve his mood. In fact, he had felt himself growing steadily more maudlin with every drink he consumed, but stubbornly, he carried on pouring the whiskey down his throat, hating himself a bit more with every sip.

Joe had just refilled his glass with another scotch when the door to the bar opened again. Mark had given up looking hopefully over his shoulder, checking out every new entrant, so took a slug of whiskey and put his glass back down on the bar clumsily, spilling a little. His mood took another nosedive when he realised who the person who just walked in was.

'Joe, good evening to you. How are you this fine night?'

Mark did his best not to scoff, but he was drunker than he had intended to be, and wasn't sure how successful his attempt to stay silent was, although Derek hadn't seemed to notice.

'I'm all right thank you Doctor Shepherd,' the bartender replied. 'What can I get you?'

'I'll have a whiskey thank you. A scotch, if you have one. Something good.'

Joe poured a drink from the same, somewhat depleted, bottle he had been pouring Mark's drinks from. It was a good whiskey, a Glenfiddich, and Mark watched from the other end of the bar as Derek savoured his first sip, letting the amber liquid sit on his tongue. Derek had always drunk good whiskey like that, as if it was some exquisite nectar, and he didn't know if he'd ever get the chance to try it again, so he had to gain maximum enjoyment from every drop. It reminded him, painfully, of New York.

'Doctor Shepherd, you seem very happy tonight, if I may say,' Joe commented. 'Can I ask what's happened to bring about this feeling of bonhomie?'

'You can indeed. I'm happy because it's been a good day, and it's about to get even better.'

'Yes?'

'Because in precisely –' Derek checked his watch, a beautiful silver Omega that Mark knew had been a twenty first birthday present from his grandfather '– eighteen minutes, Doctor Grey will have finished her shift, then she will be coming down here and I will be taking her out for a fabulous dinner.'

Derek's undisguised exultation made Mark feel faintly sick. Derek had been a lot of things over the years, but he had never been thoughtless, not until this last year. In fact, being thoughtless had been so far contrary to Derek's very character that it still surprised Mark when he was. It made his behaviour seem even more unreasonable, somehow.

'Lovely, where are you taking her?' Joe was asking.

'To Chez Maurice, for lobster and to look at the sea.' Derek named one of the best restaurants in the city, and looked mightily pleased with himself as he did so.

Mark looked down into his whiskey, trying not to talk. He didn't have anything to say that wouldn't make things worse, but he was sick of this. Fuck it.

'Do you remember the Debutante Ball?' he asked.

Derek glanced briefly across the bar, but refused to look around properly. 'I'm sorry. I don't talk to men who screwed my wife.'

Joe, instantly aware of the tension, retreated to the other end of the bar and began to stack glasses in the dishwasher with great diligence.

'The Debutante Ball, Derek. The summer of 1985. Do you remember?'

Derek knew he wouldn't shut up until he got a response. 'Yes, of course I remember. It's where I met Addison.'

'Right. Riiiight,' Mark drawled. 'Where you drank champagne, and waltzed her around the grandest ballroom in New York, then, what was it, you put your tux around her shoulders and carried her shoes and walked with her through Central Park until dawn.' He knew he was sounding really drunk now, but he didn't care.

Derek rolled his eyes. He was too happy about his later date with Meredith to let anything, even Mark Sloan, ruin it for him. 'Do you have a point with all this?' he said in a bored tone.

'Yeah, actually I do. When exactly did you become such a fucking bastard?'

'Pardon?'

'Because I always thought you were one of the good guys, you know. Great doctor, great husband, best friend. Then you weren't.'

'Oh I don't know, maybe it was something to do with you screwing my wife.' Derek felt his temper begin to slip away from him.

'And now I come to think of it, when exactly did you become so fucking righteous?'

'Righteous? She was my wife. You were my best friend, for fuck's sake, you were my brother, and I came home from work one night, and there you were, in my bed, with my wife.'

Quite a few people seemed to be staring at them, but Joe, on the other hand, was shrinking as if he would quite happily climb into the dishwasher with the glasses himself.

'Well, someone had to be!'

They were both out of their seats now, and facing up to each other. A couple of guys who were sitting at a table near the door half rose out of their seats, but Joe discreetly shook his head. These two needed to say these things to each other. Someone could intervene if the fists started flying, but not before.

'What the Hell is that meant to mean?'

'You know what it means Derek. You were never there. Never. Addison said then that you didn't come home more than one night in a week. Christ knows where you were, but it sure as Hell wasn't with her.'

'I was working, you know, saving lives.'

'Don't be such a fucking hero. You can't be proud of something that destroys lives at the same time.'

'Don't be so melodramatic.'

'Oh, so you're happy right now, are you? Well, bully for you. Because if you don't think you destroyed your own life, you sure did a fair old number on mine and Addison's.'

'Are you expecting me to feel sorry for you? Because you're going to be disappointed.'

In a split second, Mark felt all the anger just drain out of him, as if someone had taken out a plug. He wasn't mad, not at Derek, or Addison or even himself. He was sad, disappointed and sad. He even felt a little old.

He shook his head and took a step backwards, away from confrontation.

'History is written by the victors, Derek,' he said quietly.

'What's that supposed to mean?' He dropped his voice to the same level as Mark's, but his retained a cutting, vicious tone.

'The Debutante Ball. Your amazing night with the girl of your dreams. The Summer of 1985. Falling in love. Whose date was she that night? When she stood at the top of the steps and they announced Addison Forbes Montgomery, who walked down the stairs with her? Whose corsage was she wearing? Who introduced you to her?'

Derek was dumbstruck for a moment. In the dim light of the bar, he couldn't say for sure, but he thought there were tears in Mark's eyes. He sounded as if he meant what he was saying, which surprised him. He really didn't think Mark ever meant anything he said. A flash of memory forced him to relive the image of a stormy night, rain lashing against the window and a white bolt of lightning illuminating Addison's pale thighs in the darkness, wrapped around Mark's waist. Any flicker of sympathy immediately died.

'You saw her first?' he snapped. 'You've got to be kidding me. That's the most pathetic argument I ever heard.'

It was true though. Addison had been Mark's date that night. He remembered, a few days before the ball, lying on the Central Park grass in the hot sun of a New York summer. Mark was telling him about his date for the ball.

'Wait 'til you meet her. She's phenomenal. This amazing red hair, and legs all the way to Canada, I swear.'

'Where'd you meet her?'

'The tennis club. She needed some more string for her racket.'

'I bet she did.'

They'd both been philanderers back then, rather than just Mark. Seventeen, sexy and smart, they'd thought they were God's gift to the Trust Fund sponsored daddy's girls that filled the Upper East Side. Most of the girls had seemed to agree with their assessment of themselves.

'Hey, she's not like that. She's… nice.'

'Nice?' Mark had never described a girl as 'nice' before, and Derek sat up and looked down at him. 'Do you like this girl?'

'No. I don't know. Maybe. She's different, you know. She actually has a personality, and ambition. She wants to be a doctor, a surgeon. It's refreshing change from all these simpering idiots that intend to live on daddy's money for the rest of their lives.'

Mark's family wasn't rich. He had attended the same school as Derek on a scholarship, and would never have been considered acceptable without his status as a pseudo son to the Shepherds.

Derek lay back on the grass.

'Well, I can't wait to meet the girl who has the great Mark Sloan eating out of her hand.'

'You're going to love her,' Mark had said, emphatically. That was the thing with Mark; he was always right.

The guilt, which he had been fairly successful in quelling ever since he had gone to Addison's hotel room and found Mark emerging from her shower, began to flood back. Suddenly, he felt really ashamed of himself. He had every reason to be angry at Mark and Addison, but it was his fault. He'd started it. He'd started all of it. After that night, there had only been one ending, really. How had none of them realised that?

'I loved her Derek. I know you don't believe me, and I really don't care anymore.'

Derek did believe him, but he was damned if he was going to let Mark know that.

'If you loved her so much,' he said scathingly, 'then why did you screw every piece of skirt that came your way? I left. You had her, you won, and then you blew it. You threw it all away.'

'Threw it all away? Jesus, are you that stupid, Derek? Do you really think that, once I'd finally, finally got Addison to need me the most, that I'd do anything to jeopardise that?'

The anger and passion in Mark's voice made the retort die in Derek's throat. He had known Mark since they were ten years old, and he had never seen him care so much about anything.

'Because I wouldn't. I just wouldn't,' Mark said emphatically.

'Then why?'

'To make her go.'

'What?'

'To make Addison leave, Derek. You should have seen her. She pretended she was okay, but she was completely lost without you. She wasn't even a shadow of her old self; she was nothing. Losing you broke her down to nothing, and I couldn't bear to watch.'

He could see that his words were hitting home, so he pressed forward his advantage. It was all well and good leaving everything in the past, but he needed Derek to understand. And Derek needed to know the truth. Yes, he and Addison loved each other, but at the end of the day, they both loved Derek more. It was why Addison had chosen Derek, and why Mark had let her.

'She couldn't eat, she couldn't sleep,' Mark continued. 'She went to work, but she was so mechanical. I would look into her eyes, and there was nothing there. Nothing.'

Derek couldn't meet Mark's eyes. 'I never knew,' he mumbled.

'I know you didn't. I'd have told you, if I thought you would have listened.'

'I…'

Enough was enough, Mark had decided. He had made his point. Judging by Derek's stricken look, he now understood. Draining the last of his whiskey, he grabbed his coat and pulled it on.

'It's okay Derek. It's okay. Just next time you lean in close and whisper sweet nothings in Grey's ear, just because you can see Addison walking towards you, just remember.' He started to walk away, then turned back to look at his best friend, who hated him.

'Remember the Debutante Ball.'