Sherlock hums softly, nodding. Is he hovering? Maybe he's hovering. Intruding on space. Now that John's facing him he seems awfully closer, closer than Sherlock had quite noticed before, and he supposes that to an intruder it'd look as though they're up here to do the sort of things people normally seek out empty classrooms to do (which is nonsense, of course; if Sherlock were going to snog John he'd probably do it some place they'd be far less likely to be interrupted). For all his talk about decency he really doesn't care, but someone else might, and that, yes, that would be trouble. Irritating.

Still, he doesn't care to move away.

“Yes to the table. Obviously. Have to have someplace to do experiments.” Experiments on late nights; there would be, have to be, get too bored otherwise. All night, maybe; wouldn't be the first time. The thought of John joining him at sunrise, tousle-headed, rubbing the sleep from his eyes, warm and sleepy and fascinating really is unspeakably nice.

“Can't not do experiments. Might miss out on finding an even better way to get things wet, and then where would we be? Inefficient. Bad news.”