Over the last century Mauritania has made several attempts to ban slavery.

But finally, in August 2007 owning slaves became a criminal act for the first time.

Overnight, half a million people - a fifth of the country's population - were officially freed from bondage.

However many of them didn't hear the news. Without having access to broadcast media or the ability to read, and even if they had, it might not have meant much.

David Gutnick of the Canadian Broadcasting Corporation visited Nouakchott, the capital of Mauritania.