Mycroft heard his brother's deep voice in the outer office, speaking rudely to his PA. Glancing at the clock and pushing his mountain of paperwork aside, he waited.

Heavy footsteps strode toward the door. Seconds later it swung open, hitting the wall with such force that two pictures fell off their nails. Mycroft saw Anthea, who was used to this routine by now, scurry out for a rare coffee break, shutting and locking the outer office door behind her.

Leaving the Holmes brothers alone with each other.

Sherlock stood in the doorway, looking like a provoked wild animal. He was breathing heavily, eyes luminous with lust and teeth bared. Even his curly hair was more riotous than usual. Although his Belstaff coat concealed it, Mycroft knew from past encounters that he was painfully hard.

Mycroft got out of his chair and stood before the desk. He didn't say anything: Sherlock was beyond the point of rational conversation right now. He just waited for the body-slam.

Solving a challenging case always had a drastic effect on Sherlock. Normally silent and moody, he would suddenly become talkative, face lighting up with pleasure whenever he recounted how he had shown up Scotland Yard's veteran detectives yet again. He would phone and text incessantly, cackling about this or that obvious clue that their "silly little brains" couldn't appreciate. That was merely annoying: Mycroft was more concerned at the way Sherlock's dormant libido also sprang to furious life and demanded satisfaction that his own hand could not deliver.

That was why Mycroft always manipulated him into visiting the day after any case's successful conclusion. He didn't trust his wild brother to deal with that atypical sexual aggression via normal channels: Sherlock wasn't in a relationship, he decried wanking as 'boring', and he lacked the patience to arrange a rendezvous with a professional. Mycroft worried that given time, he'd snap and do something that would land him in jail and quite possibly destroy someone else's life. It was a horrible thought, but also a very real threat.

Mycroft was the only safe option.

Sherlock snarled and rushed at him. Mycroft went pliant, allowing the younger man to spin him roughly about, shove him face down onto the polished wooden desk, and twist one arm behind his back. With his other hand, Sherlock made quick work of first his brother's trousers and pants, and then his own.

Mycroft was already lubricated and partly open: Sherlock probably never guessed that his icy, remote brother had worn a butt plug all night, in anticipation of this morning visit. Mycroft knew Sherlock better than Sherlock knew himself. Always had, and that made the younger Holmes hate him more.

The elder Holmes put up an obligatory struggle before going still. Chuckling nastily, Sherlock lined himself up with the secretly lubed entrance and pushed in. When Mycroft felt that hot shaft, so long and thick, stretch his anus before sliding deep into his body, he bit his lip to suppress a satisfied groan. Sometimes he wondered whether these sessions weren't as beneficial for him as they were for his brother.

Above him, Sherlock growled. It was a deep, lusty noise that signaled his excitement and pleasure. Mycroft flexed his internal muscles and squeezed on his brother's cock, encouraging him to start moving. Sherlock shivered all over and began a mad, frantic thrusting. Mycroft pushed backward to meet each plunge, bearing down on purpose to bring Sherlock to the brink faster. Their available time was limited: he had to meet the American ambassador in half an hour, and there would be… cleanup… necessary when their rough coupling was done.

Sherlock swore. His fucking became more violent; Mycroft felt his arm being jerked painfully up and teeth dig into his shoulder. The dash of pain combined with the high-velocity attack on his prostate to send him over the edge: seconds later his cock spurted wads of hot sperm against the front of the desk. He didn't always come during these brief, fierce encounters, but when he did, the orgasms were blinding ones that made his fingernails dig into the polished wood and his mouth taste blood.

Annoyed that Mycroft had climaxed first, Sherlock gave one final, punishing thrust and began to move his hips in a circular motion, rubbing his shaft repeatedly over his brother's prostate. Mycroft felt a moment of victory when he came a second time, but his satisfied moans were soon drowned out by Sherlock's triumphant bellow as he shot his load deep into his brother's trembling body.

Mycroft did not move when Sherlock slumped against his back, pinning him. They gasped, sweated, and let their hyper-stimulated nerves settle. Then Sherlock pulled out, tucked himself back into his trousers, and re-arranged his clothes.

"See you at Mummy's for Sunday dinner- maybe," he said, voice perfectly level and flat once more.

"She'd be thrilled to see you." Mycroft got up slowly from the desk, clenching himself to keep Sherlock's release inside until he could step into the private toilet. "Thank you for coming by."

Sherlock nodded sharply and stepped out. When the door closed behind him, Mycroft closed his eyes and sighed. He knew that most people would regard these 'visits' as assaults, and strictly speaking, they were: Sherlock didn't care if his brother enjoyed himself, and frankly, he didn't mind either. Further proof that the world would never understand Sherlock, and Mycroft's obligation was for life.