Variations of this scam have been going around now for years- the con used to be sent either by letter or fax. Now, over the past few years by email. The scam invariably has an African country's origin, which is one of the main clues, and the kicker is that they always mention that they will require bank details, or a deposit, from you, before they can send you on the share of +-£100m(- not!). Once they have your money, you will never hear from them again.
The emails usually seem so unbelievable. Some emails are quite funny, they're so badly put together. You would expect that the practice must be known to just about everyone by now, but- yet, one reads of people being taken in all the time.