The first 'official' detective of Detective Sunday is Detective Superintendent Roy Grace from the Roy Grace series written by Peter James. I derived the style of David Lloyd's 'Kickback'.
I'm getting to know quit a few detectives from the novels I've read. All of the characters have something distinctive, and so has DS Roy Grace. His girlfriend has been missing since he was thirty and he sometimes consults a medium to help him solve his cases. But compared to all the other detectives, Grace seems most natural to me. That was the first image that I came up with and tried to create. Just a regular man. But a most driven detective.