Apparently this joke was told by Kenneth Kaunda, President of Zambia, to P.W.Botha when he was President of South Africa, at one of their meetings in a train at the Victoria Falls. I saw it in a newspaper. P.W.Botha calls an old friend, a white farmer in Zambia. "Hello, Marius old friend, how are you these days?" "P.W.! I haven't heard from you for years. Well, you know, can't complain. And you? What are you doing?" "Me? Not doing too badly. I'm the President of South Africa." "President? You poor man. Now, up here, we have a black to do that job..."
(From the "Rest" of RHF)