Disclaimer: I do not own Sherlock.
John wasn't entirely sure how he'd ended up here. Two weeks ago he hadn't been dating anyone, let alone a man, and then Sherlock-sodding-Holmes had proposed marriage out of nowhere and, well, everything had sort of clicked into place. He'd always heard it said that an impetus was required for two best friends to realize they're in love. Evidently, the very-intelligent John Watson (although he was doubting his intelligence now, certainly), had needed a fairly large one.
And so here he was with Sherlock in front of him, Lestrade behind him as best man, and Harry dabbing her eyes in the pews and insisting that she'd seen in coming all along.
Really, it was perfect. John wasn't an overly-romantic man, but Mycroft really did have excellent taste in wedding decorations, or at least he knew how to hire people who did. Everything was white and tasteful and, John supposed, wedding-y,
Everything except the asshole John was apparently madly in love with and had agreed to marry for reasons passing understanding.
"I'm bored, John," Sherlock said a bit too loudly for John's taste, considering they were at the altar at the moment. "How long are these things supposed to take?" The preacher frowned but didn't break his stride.
"It's our wedding, Sherlock," John hissed. "It'll take as long as it needs to."
The preacher went on for a while about love in all its splendor and John was finding it all very touching until he noticed that his very-nearly husband had dropped his head back (the rest of his body still posed perfectly and, quite frankly, stunning in his tux) and was staring at the ceiling.
"Get out of your mind-palace! You're getting married!"
"But I'm bored," Sherlock whispered back loudly.
"I'll divorce you."
"You can't divorce me, we're not even married yet!"
"I'll find a way, don't think I won't."
"Marriage isn't to be entered into lightly," the preacher said louder than was probably strictly necessary, looking at them for longer than was probably required. "It is a sacred undertaking that..."
Sherlock grumbled under his breath. "Yes, yes, why would I undertake it if I didn't know the definition of it?"
"Sherlock. Shut up and enjoy the happiest day of our lives!"
"When two people are absolutely certain they will love each other for the rest of their lives-"
The detective rolled his eyes and John prepared to punch him if necessary. Apparently his glare kept his genius under control, however (maybe this marriage would work out?) because instead of making a comment he just rolled his eyes again and bit his tongue.
"...as long as you both shall live?"
"I do," Sherlock said. He couldn't help but add, "Why would I have asked John to marry me if I wasn't certain I would love him until I died? Honestly, you just keep repeating the definition of-"
"Shut up," John snapped without venom. (No venom because it had been a pretty cute statement, actually, and since it had been an accident John could be sure he meant it.)
"Then by the power vested in me, I now pronounce you partners."
"Finally!" Sherlock said at full-volume, making no one but the preacher jump since the rest of the people present knew him. "Come on, John!"
Sherlock grabbed John and dragged the man, not pleased but entirely unsurprised, by the hand, hailing a cab and ordering it to 221B.
"I left an experiment on the stove," he explained once they were seated. "I estimated twenty minutes for the ceremony so I can't imagine what has happened to it with an extra forty-three minutes at such a temperature..."
It was all very unorthodox and John pretty much hated his husband.
Conveniently, he thought as he sat back in the cab, a little worried that he'd find an acid-hole in the floor of their kitchen when they got home, he'd also have it no other way.