You understand that Billco is a small company with no real reserves and if you were to sue them for the amount you are losing as a large corporation, they would simply go into liquidation. You do have a personal guarantee from Polkinghorne, but again, compared to the amount involved, this is meaningless. You also don't really want to pursue him in the Brazanian courts as they are hopelessly inefficient and issuing proceedings in Britain would cost a fortune and be enormously inconvenient, again with little prospect of any real financial gain even if you were successful. This is why you have turned to mediation as a last resort.