Since the very first episode. Sources: (x) (x)
I am all for johnlock, but it always sort of irks me when these shots are presented as any kind of evidence, mostly because they are always presented without context and thus appear extremely misleading.
Take the first scene - it was a pretty intimate moment indeed, but for completely different reasons: Sherlock was just admitting his past drug problem and John had trouble believing it. There is no sexual subtext in this, only John’s disbelief and Sherlock’s I-dare-you-to-say-a-thing!
As for the lips licking - yeah, excitement is one of the possible reasons. And even excitement can have loads of different causes than sexual attraction. Adrenaline rush anyone?
Besides, Martin is licking his lips constantly - it’s his habit and therefore it fails as a proof of anything. He does it all the time, even as Bilbo. And I do not think we need to suspect good old Bilbo when it comes to sex.
I just wish there were more posts about real tender moments between these two, not phony evidence that only serves as a crowd pleaser with a potential to delude people who have not yet seen Sherlock.