Who is Charlie Gotso from The No. 1 Ladies' Detective Agency and what is their importance?

Charlie Gotso is something of a shadowy figure in the narrative, portrayed (mostly through the opinions of other characters) as politically and financially powerful, a Mafia-like figure in the background of much of what goes on in Botswana. This sense of power and influence is highlighted and/or illuminated by the fact that he is spoken of more than he actually appears, with the way in which he's spoken of reinforcing his reputation even further. His only appearance (in Chapter 18) gives the impression that the ways in which people view him (primarily with fear) are quite justified, in that he seems both ruthless and self-interested ... but not smart enough or tricky enough to evade the manipulations Mma Ramotswe puts him through to get to the truth of her investigation.