What is the function of the inspector in 'An Inspector Calls' by J.B Priestley?

The Inspector "need not be a big man, but he creates at once an impression of massiveness, solidity and purposefulness." He is in his fifties, and he is dressed in a plain dark suit. Priestley describes him as speaking "carefully, weightily ... and [he] has a disconcerting habit of looking hard at the person he addresses before he speaks." He initially seems to be an ordinary Brumley police inspector, but (as his name might suggest) comes to seem something more ominous--perhaps even a supernatural being. The precise nature of his character is left ambiguous by Priestley, and it can be interpreted in various ways.In any case, the inspector is able to draw the characters in the play out thus revealing their true motivations.