Genocide is often called the ultimate crime and after every tragedy, the world says 'it must never happen again'. And yet it does. Hardtalk speaks to leading international human rights lawyer Payam Akhavan, who made his name trying to bring to justice those responsible for war crimes in the former Yugoslavia. He believes that the international community has a duty to challenge human rights abuses wherever they occur. But is true justice ever really possible - or is it compromised by the political constraints and realities of the day?