"You all know about population growth. When Oxford University was founded in the 13th Century there were about 500 million, people in the world. When the Open University was set up there were 3 billion and when we celebrate our thirtieth anniversary at the end of this century there are likely to be 6 billion. To situate the same phenomenon ... in Africa you only have to note that in 1960 there were only three African cities with populations......