Jim smiles too, not to himself. He's aware, vaguely, that they're drawing attention but he couldn't give a damn. At least some of it's positive, and some of it probably isn't, but he's tuning it all out.

When Sherlock draws away he just puts his back against his chest, and leans against him again. Let them try to interfere with the two of them. Jim won't stand for it. He's not in the mood to indulge the world being stupid today.