Assuming you're right and it was just prospecting - it seems odd that prospecitng was ongoing for 12 years by  the way - why then:
1) Lie about it, and even have the Botswana government officially deny it's happening until confronted with undeniable proof ? 
2) Cover it in a heap of shell companies to try and hide the true ownership and capitalisation of the project ?

Secrecy always smacks of corruption. Private citizens have the right to privacy. Public companies do not - by definition their every action is a matter of public interest and we the people have a right to know all about them - including and ESPECIALLY the movement of every penny that ever passes through them.