By Barnaby Phillips
BBC correspondent in Johannesburg
The president of South Africa and the king of Lesotho are attending the official opening of an enormous dam and water project in the Lesotho highlands.
The dam project led to a flood of corruption allegations
The first phase of the Lesotho Highlands Water Project has now been completed - two enormous dams have already been built and work on other dams is expected to continue for many more years.
The project, which has cost billions of dollars, is intended to channel water from the highlands to industries and cities in South Africa.
But it has also drawn attention to the corrupt practices of some Western companies working in Africa.
A local official in charge of dam construction was sent to jail after he was discovered to have money in secret Swiss bank accounts.
The Lesotho government did not let the matter rest there.
It took action against the Western construction companies which it believed were complicit in the corruption.
It has successfully prosecuted Canadian and German companies and it is now investigating companies from Britain, France and other countries.
Whilst African leader are often - and with good reason, accused of corruption - Lesotho's government has made out a persuasive case that Western companies are frequently involved.