As Brazil prepares to host the next World Cup, its people are confronted with the growing problem of child prostitution. The country's relaxed attitude to buying sex has long attracted millions of tourists, particularly men. But now the world's oldest industry is recruiting the world's youngest workers. UNICEF estimates there are 250,000 children forced into prostitution across Brazil. In this shocking episode of Our World, Chris Rogers goes undercover, posing as one of the millions of so-called sex tourists who visit the South American country in search of cheap sex, often with children as young as seven years old.