Nigerian scam hits my postbox

Somebody obviously got hold of my office contact details, because I received a letter from one of those Nigerian fraudsters today. A paper letter, not an e-mail. Signed by a human hand.
The stamps from the letter came from Cameroon, but the author claimed to represent a Nigerian petroleum company. The amount was US$30 million and I was promised 20% of it for helping him transfer the money.
It is really dodgy.
[ Update: Here’s a scanned copy of the letter in question. ]