1. Mrs Hudson
The final name on this list goes to Mrs Hudson. Mrs Hudson is a vital part of Sherlock mythology and so needed to be a vital part of the BBC's adaptation of Sherlock. She can almost be seen as the mother figure that Sherlock sorely needs at times. Mrs Hudson is the glue that holds Holmes and Watson together. She looks after them when she's needed but knows when to leave Sherlock alone. The pair hold her in incredibly high regard. They strongly chastise characters who insult her and they both leap to her defence when she is attacked in A Scandal in Belgravia. She also provides much needed comic relief in a show that is often full of dark tones. Her lengthy rant at Sherlock's gravestone provides a laugh right after we have apparently witnessed the suicide of Sherlock Holmes. The show needs this kind of light touch and so Mrs Hudson is one of the most important, and underrated, characters on the show.