Dispatches reveals the tragic consequences of first cousin marriage in Britain. Every year such marriages cause hundreds of children to be born with terrible disabilities; one third of whom are so ill that they die before they are five years old. The practice is most common in Britain's Pakistani community, in which more than 50% of people marry their first cousin, and in Bradford 75% of ethnic Pakistanis follow the tradition. It is also common in some Middle Eastern and East African communities, and in the UK's Bangladeshi community, nearly a quarter of people marry their first cousins. It also happens in the white British community. Journalist Tazeen Ahmad meets families affected by degenerative genetic disorders associated with first-cousin marriages. As a grandchild of a couple who were first cousins, she examines the medical risks, which include infant mortality, birth defects and learning difficulties, and asks why there has been no major publicity campaign to warn the public about the dangers of such relationships.