Prime Minister Tony Blair is in South Africa on the final leg of his farewell tour of Africa.He arrived in Johannesburg following an overnight flight from Sierra Leone after attacking the "cynicism" of critics who described his diplomatic mission to the continent as a "vanity expedition".Mr Blair delivered a passionate defence of his interventionist foreign policy in a speech at the University of South Africa Business School in Midrand, near the capital Pretoria.He called for greater urgency from the international community to stop the bloodshed in the Sudanese province of Darfur and restore normality to Zimbabwe.And he insisted that intervening to assist the poor nations of Africa was not only morally the right thing to do but also in the self-interest of the rich world.Mr Blair said Africa was a subject "close to my heart" and had been at the top of his foreign policy agenda throughout his decade in power."Above all, and most controversially, Africa has been a prime example of a foreign policy that has been avowedly interventionist," he said."I believe in the power of political action to make the world better and the moral obligation to use it."I don't believe that in this time, in the early 21st Century, international politics can be just about nations' interests, narrowly and traditionally defined."I believe that now, today, our self-interest is in substantial part defined by the well-being of others, that the consequence of globalisation is that our best chance of security and prosperity lies in advancing freedom, opportunity and justice for all."Mr Blair will later meet former South African president Nelson Mandela and will have talks with President Thabo Mbeki tomorrow.© Independent Television News Limited 2007. All rights reserved.