Benedict has known Una Stubbs (Mrs. Hudson) his entire life because she is a close friend of his mother. So the affection Sherlock shows Mrs. H is completely real and completely Benedict's doing (Moffat didn't write it in initially). << that is precious!!!!
I’m sworn to secrecy about the plot of the new series, but one thing I can tell you is that my character has a lot more to do in it. New Una Stubbs S4 Sherlock interview - ( x ) Making tea, foreshadowing, and kicking the arse of the British Government