I have to say, one of my favourite things about the bbc Sherlock is this. Sherlock has been characterised as a ‘master of disguise’. Most versions of Sherlock take this in the most obvious sense (think RDJ’s Sherlock in the nearly indecipherable disguises).
But BBC Sherlock? He’s still a master of disguise even though he rarely changes any aspect of his outfit. The closest he came was the clerical collar and even that was the smallest of additions to his usual costume. BBC’s Sherlock is a master of disguise but not through any costume changes - it’s through body language.
And that really mirrors who he his. Every Sherlockian knows the line “No what I do is notice.” (and various paraphrases) and that’s what Sherlock uses - he knows what movements and expressions cause people to subconciously react in certain ways. BBC’s Sherlock is an elite master in disguise because he doesn’t need anything but himself.