Millions of documents have been leaked which show how some of the world's wealthiest and most powerful people have been able to launder money, dodge sanctions and avoid tax. Eleven million documents from the offshore finance specialists Mossack Fon-seca have been released -- making it a bigger data leak than the Wikileaks revelations. Mossack Fonseca, which is based in Panama, has denied any wrongdoing. Our special correspondent Richard Bilton reports.