Why tax? Why now? And what impact are we having? Poor countries have the riches to help work their own way out of poverty. But a worldwide culture of financial secrecy allows some unscrupulous companies to dodge tax and rob poor countries of more than $160bn a year. Here David McNair, Christian Aid's Senior Economic Adviser and Rachel Baird, Policy and Campaigns Journalist talk about why we should work on tax now, and the major success of seeing tax internationally recognized as a key factor in meeting the Millennium Development Goals.