What is the difference between a war crime, a crime against humanity and genocide? And who holds those responsible to account? Anna Holligan, the BBC's correspondent in The Hague, gives an insight into how the International Criminal Court works. She shares some of the cases of those who have been charged with the gravest crimes of concern to the international community, from Congolese warlord Thomas Lubang to Bosnian Croat war criminal Slobodan Praljak.