Who is Chief Inspector Parker from The Nine Tailors: Changes Rung on an Old Theme in Two Short Touches and Two Full Peals and what is their importance?

Chief Inspector Parker is a member of the CID who works with Lord Peter to trace and interview various suspects. He is familiar with criminals and their ways, and his interaction with Nobby Cranton is not particularly antagonistic - in fact, Parker seems remarkably tolerant of Nobby's impertinence. However, he does not quite have the sympathetic and empathetic imagination of Lord Peter Wimsey.