AN: Okay, so I've written this as if Meredith and Derek never got together and that in fact he got into a relationship with Mark so I guess it could be considered an AU. All the background story is the same really (SPOLIERS!) Derek told the board about Webber's alcoholism and he was appointed the Chief, Mark is an attending at the hospital.

The Chief's Chair

"So you're the Chief." Mark said to Derek, standing in the doorway, watching as he threw the mini basketball at the hoop and missing.

"I am. Are you okay with that?" Derek said, looking back at him.

"Of course. Besides, you look hot in a tie." Mark replied, entering the office and grinning. He and Derek had been dating for a while now, almost two years in fact and even now he was sometimes knocked sideways by just how good-looking Derek actually was. He had the perfect hair, perfect smile, perfect body and his breath stopped every time Mark realised that this man, this surgeon was his. He was smart, kind and gentle but firm when he needed to be and now that he was Chief, well things would be changing.

He caught the ball as Derek missed again, throwing it and laughing as it flew through the hoop.

"Fluke!" Derek cried, laughing too.

"No way. I'm just that good."

"Whatever. You know, Hunt got me this as a present, Torres got me a bottle of very expensive whiskey and Robbins made me a cake. But you, you haven't gotten me anything."

"Oh I've got something planned." Mark told him, smirking mischievously, before stepping up to Derek and placing a quick kiss on his lips.

"Oh yeah? What is it?"

"That'd be telling. Although I'm pretty sure having me for a boyfriend is a good enough present."

'That isn't a present! That's just…well, that's just Heaven." Derek said, smiling at Mark and stroking his arm. "I do love you and I hope this thing, becoming Chief. I hope it isn't going to affect us. You sure you don't mind?"

"I'm sure I'm sure. Honestly." Mark said, felling his chest swell at Derek's words. "and I love you too."

They threw a few more hoops, leaning against Derek's desk and chatting about their day before Mark won and started to gloat. Derek punched him lightly in the arm, laughing before throwing the basketball one last time. It hit the rim and flew onto the coffee table, knocking medical journals all over the floor. Mark headed over, cleaning up the mess and throwing the ball on the couch and turning back to Derek. He drank him in and felt himself growing hot, his tongue coming out to slowly swipe over his bottom lip. They hadn't been able to see each other all day, Mark busy with back to back surgeries and Derek adjusting to his new role. Normally they'd manage a quick fumble in the lift, or a hurried blowjob in the on call room but not today and Mark was now feeling the effect.

"So you really think I look hot in a tie?" Derek asked, smirking and noting Mark staring at him.

"So hot." Mark told him as he walked towards him.

Mark tugged Derek's tie, pulling the other man towards him, their bodies pressing together. His other hand slipped up onto Derek's waist, holding him gently before their lips touched. The kiss was long and sweet, Mark's tongue slowly slipping into Derek's mouth as they tasted each other. Soon enough it became more passionate, both their movements speeding up. Mark moaned into Derek as he felt those strong hands slide over his biceps, over his shoulders and around to his back where they rested upon his shoulder blades. He could feel the heat from those hands melting through the thin scrubs.

Derek gave a sigh as Mark pulled away from his mouth, that sigh turning to a soft moan as butterfly kisses were placed along his jaw and down to his neck. Mark kissed the soft skin, nipping at the flesh occasionally and enjoying the taste. Derek's hands slid downwards, his hands roaming over the planes of Mark's back before slipping under his scrubs and stroking him. Mark groaned into Derek's neck as he raked his nails down his spine, a shiver of lust coursing through him. Mark, wanting to tease Derek for the scratching slipped his hand between the two of them, the hand holding Derek's waist moving towards his crotch. He groped the hard length, both of them moaning as it throbbed in his hand. More kisses were placed on Derek's neck and jaw as Mark switched sides, wanting to nibble on him some more. He kept up the groping, building up a rough rhythm on Derek's crotch, pleasuring him through the layers of fabric. Derek's groans filled his ear as he picked up the pace some more, that hot breath tickling his skin.

"Mar…Feels so…good." Derek whispered to him, his hands still tracing lines up and down Mark's back, those strong digits massaging his muscles. He continued lapping at Derek's neck, biting and kissing his way up and down. In one swift movement Mark pulled the zipper on Derek's pants down and slipped his hand inside, massaging the large bulge that he found, groaning internally at the heat that was emanating from it. Derek gasped as Mark's fingers worked him up and down, both of them groaning as they found the wet spot at the top of the bulge.

"Gotta…you…gotta get me off Mark. Need it." Derek whispered to him and for a few moments he was tempted, but then his eyes fell upon the chair. The Chief's chair to be exact. He'd only been in this office a couple of times but when he had The Chief had been sitting in it and he could feel the power radiating from it. The only person who sat in that chair, who was meant to sit in it anyway was The Chief, the one who oversaw everything. He was in charge and he commanded everyone and as of today that man was Derek. He groaned to himself as he thought of Derek in that chair, giving orders and talking to people in that demanding tone he had. Whenever he heard him using that voice Mark felt himself growing hard, he didn't need to do anything, didn't even need to touch himself. Derek just had to speak, no command and he was hard.

"Derek." Mark managed to say, kissing his way back up his neck before reaching his jaw. He slowed his hand movements down, a whine escaping Derek's mouth as Mark just held him. "This might sound strange. But can you sit in your chair?"

Derek leaned back and looked at Mark, grinning before giving a chuckle when he realised Mark was serious. He glanced over his shoulder at the chair, his hands coming to a halt at Mark's lower back, before he turned back around.

"Why?" He asked smirking.

"Just…cos."

"Just cos? You're going to need to give me a better explanation than that!"

"Come on. Just sit in the chair. It'll be hot." Mark told him, frowning slightly at how strange he sounded. Derek stared at him for a few moments before laughing some and shaking his head. He pulled back from Mark, whose hand slipped out of his pants whilst his own slipped out from under his t-shirt and walked around his desk to the chair. Derek grabbed his white coat, starting to pull it from his shoulders but Mark stopped him.

"Leave that on too." Derek stared at him some more; wanting to see if he was serious again and when he decided that he was he plopped down onto the seat.

"Now what?"

Mark licked his lips as he took in the sight of Derek behind the desk, resting his hands on his stomach and swinging the chair side to side slightly. He looked powerful, strong and commanding. If anyone walked in now, wanting to complain about something or starting up with some bullshit Derek would handle it gently but firmly. He'd tell them what to do, Hell he could tell anyone what to do and whatever he decided that would be the final decision. Nobody could rise above him, nobody could say no and Mark was a little disturbed by how turned on that thought made him. He walked around the desk and slipped between Derek and his desk, their legs pressing together. Derek smiled and leaned forwards, his hands coming up to stroke over Mark's thighs, his eyes lingering on Mark's crotch.

"Mmm, I like where this is going."

"No, no, no." Mark told him, batting Derek's hands away. "You said before I never got you a present. Well, I'm thinking a little dirty office sex is the perfect present."

Derek's eyes widened, automatically flicking to the door and to the window before coming back to Mark. He licked his lips as his eyes roamed up and down Mark's body. Mark felt another one of those shivers, this one going straight to his cock as he realised that Derek was eyeing him up and imaging him naked. After all this time together he could read him like a book and those eyes, he could see lust dancing about in those eyes and he twitched at the thought of what Derek was thinking. Derek however grinned but shook his head.

"We can't. Anyone could walk by and see us!"

"So?"

"Look, I'm all for dirty office sex. But getting caught having dirty office sex on my first day as Chief is not how I want to be remembered."

"Come on. It'll be quick…hot...dirty." He said, leaning down and kissing Derek. Their lips moving against each other and tongues instinctively touching. As they kissed Mark slid to his knees, spreading Derek's legs and sliding his hands up over those muscular thighs. Derek moaned into his mouth as Mark once again began groping him. After a while he pulled back, his hand slowly massaging Derek through his pants as he stared up at him.

"Mark, we shouldn't, we ca-"

"You're in control. This is you're hospital, you're the one who decides what to do now. You give the orders and people will listen to you. I'll listen to you. So…tell me what to do Chief."

"Fuck." Derek whispered. He stared down at Mark, biting his lip before taking the plunge. "Suck me."

"Yes sir." Mark said, winking. He reached into Derek's pants and after a little fumbling managed to pull his throbbing cock out. They both groaned and before Derek could change his mind Mark leaned forwards and swiped his tongue over the glistening head, lapping at the precome and tasting that hot taste. His tongue flicked all over the sensitive glands causing Derek to groan and bring his hand up to rest in Mark's hair, his grip strong but not painful. He carried on licking and lapping for a few moments, teasing Derek and pleasuring him at the same time but soon enough he felt pressure on his head and realised Derek was pushing him downwards. He fought for a couple of seconds, his tongue lapping at the slit and gathering more precome before he relinquished and swallowed the other man down.

Derek bucked up into him, groaning loudly as Mark took almost all of him into his mouth, stopping before he went down his throat. Deciding to fuck taking it slowly Mark pulled his head back, pulling all the way to the tip before swallowing him again. He kept this up, quick and fast, his mouth hot and wet around Derek's throbbing cock and soon enough he had him moaning and squirming in the chair. Mark wrapped his hand around the base, keeping up with the rhythm of his mouth. Derek's other hand came to rest in his hair too, both hands gripping tightly. The taste was magnificent, exquisite and individual and all Derek and he swallowed it all down. Derek was big, damn big and thick too and Mark soon found it difficult to breath. He slowed down, enjoying the whimpers and moans that reached his ears as he slowed right down, and gathered his breath. He looked up and saw Derek watching him, his eyes dark and half lidded with lust, the pupils blown. His other hand slipped up Derek's thigh, squeezing the muscle before slipping into his pants and fishing out Derek's balls. He rolled them in his hand massaging and playing with them as he sucked on the man he loved. His dexterous fingers pulled more moans from Derek as he fondled him and be brought the pace back. Going from nice and slow to hot and fast in a matter of seconds. This time however he took Derek right down, right into his throat and judging by the way the other man pushed upwards, lifting his hips off the chair he was doing a damn good job.

Mark felt his own cock throb in the tight confines of his underwear and scrub pants, groaning first at the taste in his mouth and then the pulse of his own lust. He brought his mouth off Derek's cock, watching for a few moments as it throbbed, covered with his spit.

"Wha…why…?" Derek tried to question but before he could manage anymore more groans flew from his mouth as Mark's expert tongue was on him again, this time teasing and licking his sack. Mark's free hand has slipped down and released his own cock, jerking himself off in time with the movements of his other hand. That hand was still wrapped around Derek, pumping up and down. Smell and taste hit him at the same time, both were musky and hot and manly. It was Derek. All Derek and if it was possible he could taste and smell this forever. However the Chief wanted something different at that moment. His hand releasing Mark's head and coming to rest over the hand wrapped around his own cock.

"Mark, I said suck it." It was that voice, the voice he loved and desired. Mark looked up and saw Derek staring down at him, defiant and in control. He pointed his cock at Mark, running the head over his cheek before letting it come to rest on his bottom lip. "I said suck it." That commanding voice came again and Mark didn't ignore it.

Their eyes locked as he started again, a fast and rough rhythm that would probably leave him hoarse for a couple of days but he didn't care. Didn't give a shit when it was Derek telling him to what to do and so he kept sucking and those moans and groans filled his ears. The simple knowledge that he was making Derek feel like this, making Derek make those noises was getting him off and he felt himself grow close. His cock gave a twitch and before he knew it his seed started to shoot out, splashing over his hand and his scrubs. Mark's loud moans were muffled, but the vibrations from his throat ran through Derek's cock and into his very being and he gave a cry as he let go. Hot come filling up Mark's mouth and coating his tongue. Derek grabbed his cock, pulling it from that hot cave and letting the last few spurts fly onto his face, landing on cheek and chin. They were both gasping for breath, chests heaving and cocks aching. Mark swallowed and lapped at the come, the streaks he could reach where quickly licked up and he strained to reach the others. Derek watched him for a moment, biting his lip and almost coming again just from the very sight before leaning forwards and cupping Mark's jaw. They stared into each other's eyes, blue meeting blue, before he leaned forwards and cleaned Mark up. They kissed again, tongue sliding over the other. Derek then pulled back and glanced downwards as he saw the mess Mark had left on his scrubs. He also saw his hand and reached down, bringing it up and licking that clean. Another kiss, this one soft and loving, sealed their lips together as both their hands entwined.

"That was…fantastic."

"Yeah."

"God, I love you."

"I love you too." Mark told him, nuzzling Derek's thigh and giving his hand a squeeze.

"You know if this is what you're going to be like whenever I sit in this chair. I'm going to be spending a lot of time in here." Derek said, laughing and tucking himself away.

"Hey, sounds good to me. Just as long as we christen the desk next."