Naturally this is one of Holmes's principle concerns, and it isn't because he fears for his own reputation and safety, but because -- and this is becoming increasingly obvious -- he couldn't bear to be torn away from Watson. What would make him feel better, actually, though it would be so very foolish, would be terrible... but would it be so terrible to ask Mycroft what he might be able to do in the event of Watson and Holmes's discovery? Having a plan would make Holmes feel much more at ease.

He doubts that would ease Watson's tensions.

"Thankfully we can rest assured in the knowledge that the Yard is incapable of discovering anything of use." He smiles, hoping his joke will ease the situation. "And as for Mrs. Hudson... we shall have to be particularly careful. An extra set of your clothes in my rooms, always keep dressing gowns at hand. And keep the door locked as much as possible."

He's coming back from his moment of surprise and tension, realizing that divulging hadn't been that bad, after all. He will have to tell Watson these things at some point, so it's good if he starts mentally preparing himself. He resumes his touch against Watson's jaw, unable to keep from touching him any longer.