Complex sentence: Mycroft has a unique civil service position as a kind of human database for all aspects of government policy but lacks Sherlock's interest in physical investigation, preferring to spend his time at the Diogenes Club.
Split into simpler sentences: Mycroft has a unique civil service position as a kind of human database for all aspects of government policy. He lacks Sherlock's interest in physical investigation, however, preferring to spend his time at the Diogenes Club.