Three years was a long time to be away from one's home, longer still when you lived a waking sleep and could no more understand the language of your surroundings than you could speak it.
Sometimes he felt like a ghost and wondered if he had died that afternoon at St Bartholomew's, then Mycroft would text, two or three words, and he'd remember that he was human, living, that he should eat and remember to sleep, and that one day, he'd get to go home.
Mycroft failed to tell him that he no longer had a home to go to.
Maybe Mycroft hadn't heard the old saying; what was it? A house is more than bricks and mortar and clay. Or the other, Home is where the heart is, though Sherlock hadn't got a heart, had he? Then of course Christian Morganstern once said that Home is not where you live, but where they understand you, and in that respect, perhaps Sherlock had never had a home, not once.
Three years away from London was enough however. Three years away from familiarity.
Knowing that everything a