Who is Sergeant Davies from A Test of Wills and what is their importance?

Sergeant Davies is employed at the Upper Streetham Constabulary. His superior, Inspector Forrest, assigns him to assist Rutledge in the investigation. Davies provides a list of suspects, witnesses, and information about the scene of the crime and the condition of the body. He is professional in manner and does everything by the book, though, he is bothered by the fact Forrest called in Scotland Yard.