Greg has a video on his phone of Mycroft sucking him off. He keeps it on his phone for retribution in case Sherlock steals it. The only people who know, though, are Greg and Mycroft. Until one night at the pub, after a few pints, Greg and John start talking about past hookups and things they’ve done that aren’t their norm. And Greg tells him that he and Mycroft made the video. And that even though it’s main purpose is to punish Sherlock, it’s still damn sexy to watch.
Over the next couple days, John can’t get the idea of the video out of his head. So when he sees Greg’s phone sitting on his desk in the Yard, he slips it in his pocket when no one’s looking. He figures he can blame Sherlock when he returns it later.
When John goes home that day, he goes straight to his room and locks the door. John watches the video and imagines that his is the cock coming in from the bottom of the frame, and his hand is Mycroft’s mouth moving deliciously over the shaft. He mutes the video to make the fantasy a little more real. He nearly cums when Mycroft looks up toward the camera and smirks. When Mycroft starts deepthroating Greg, John has to bite his lip to keep from shouting any names.
John knew of his crush, but now he’s not sure he’ll be able to look Mycroft in the eye without getting hard.

John answers the flat door one morning to find a tall navy captain standing in full dress blues before him. Military training kicks in and he automatically salutes the man.

“At ease.” The Captain chuckles, returning the salute. “I’m looking for William.”

“I’m sorry, there’s no one here by that name.”

The Captain knits his eyebrows, “This is 221b Baker street, isn’t it?”

John nods.

“That’s weird, then wh- Oh.” The Captain smiles and shakes his head, “No. It’s um… Sherlock. I’m looking for Sherlock. Sherlock Holmes.”

“Oh.” John says surprised, “Uh, yeah. Um, come on in. Make yourself comfortable.” He says gesturing to the client chair, “I’ll just go get him.”

John walks down the hall and into Sherlock’s bedroom. He shakes Sherlock’s shoulder to rouse him.

“Sherlock get up. We’ve got a client. I think.”

“Don’t care.” Sherlock says, rolling over.

“Get up and get dressed.” John says, snatching the pillow from under Sherlock’s head and leaves the room.

John reenters the living room to see the Captain sitting on the sofa.

“He’ll be out in just a minute. We weren’t expecting anyone so early.”

The Captain nods, “I’m sure he’s not expecting me at all.”

John opens his mouth to question the man when Sherlock starts speaking as he comes down the hall,

“This had better be an incredible case. An eight, at least. Otherwise I’m-”

Sherlock stops dead in his tracks as he sees the military man stand up from the sofa.

“Hi Will.” The Captain says, smiling a soft bright smile at Sherlock.

Suddenly Sherlock is across the room and throwing his arms around the Captain’s neck and pulling himself up onto his toes for a passionate kiss. John’s eyes go wide as the Captain wraps his arms around Sherlock’s waist and they continue to kiss. After what seems like an eternity to John, the two pull apart enough to breathe.

“And here I thought you said you wouldn’t miss me at all.” John hears the Captain whisper to Sherlock. “I think we’ve confused your flatmate. He doesn’t seem to know who I am.”

“I may have forgotten to tell him. It’s hard to keep track.” Sherlock says, keeping his voice low so as not to yet disturb their hushed peace.

“You have a tendency to talk to people when they aren’t in the room, Love.” The Captain gives a brief kiss to Sherlock before looking at John. He unwinds his right arm and extends it towards him, “Victor Trevor. It’s a pleasure to finally meet you, John Watson.”