- "Anderson, don't talk out loud. You lower the IQ of the whole street."
- ―Sherlock Holmes to Anderson [src]
He appears at a Brixton crime scene. Like other members of the team, he openly despises Sherlock Holmes. The feeling appears mutual, as Sherlock dismisses Anderson's suggestions and forces him to face away from him when he is trying to think. Anderson is married, but Sherlock deduces that he has been having an affair with D.S. Sally Donovan due to Sally smelling of his deodorant and "the state of her knees". Anderson takes an energetic – even leading – role in the drug search conducted in the Baker Street flat. 
A bedraggled and slightly unstable Anderson attempts to convince Lestrade that Sherlock is still alive, citing a pattern of cases across Asia and Europe that would have required Sherlock's intuition to solve.
He is correct in believing that Sherlock faked his death, but his theories on how he did it are incorrect. He has also founded "The Empty Hearse", a fanclub about Sherlock. 
He appears in Sherlock's apartment along with another member of Sherlock's "fan club". They have been summoned by Mycroft to search Sherlock's flat for signs of drugs, but are sent out after Sherlock mentions Charles Augustus Magnussen. Despite his seeming unimportance to Sherlock, he is there alongside Molly in Sherlock's mind palace, helping Sherlock to survive being shot by Mary. 
Anderson was cynically considered unimportant by Sherlock Holmes, but did show some degree of intelligence. He was antagonistic and borderline cruel to Sherlock, a trait shared with Sally Donovan, however he was, in some ways, just as melodramatic as Sherlock himself. Despite his arrogance, he had a deep degree of regret as he saw that his antagonism towards Sherlock was what had led him to the roof with Moriarty, to fake his death.
- In the "Unaired Pilot", he is shown to have a beard. In Series 3 he has the beard again.
- According to the Casebook, his first initial is S. This was proved wrong when his name was revealed to be Philip, in Series 3, "The Empty Hearse".
- According to a tweet by Mark Gatiss, his first name is Sylvia. However, Gatiss was not being serious.
- ↑ Moffat, Steven (writer) & McGuigan, Paul (director). (25 July, 2010). "A Study in Pink". Sherlock (2010). Series 1. Episode 1. BBC One.
- ↑ Gatiss, Mark & Moffat, Steven (writers). (24 December, 2012). "Many Happy Returns". Sherlock (2010). Series 3. BBC One.
- ↑ Gatiss, Mark (writer) & Lovering, Jeremy (director). (1 January, 2014). "The Empty Hearse". Sherlock (2010). Series 3. Episode 1. BBC One.
- ↑ Moffat, Steven (writer) & Hurran, Nick (director). (12 January, 2014). "His Last Vow". Sherlock (2010). Series 3. Episode 3. BBC One.
- ↑ (2012-02-13). "Mark Gatiss' Twitter".