Two figures have dominated the politics of southern Africa in recent years. One is Zimbabwe’s 93-year-old President Robert Mugabe. The other is South Africa’s 75-year-old President Jacob Zuma. Now Mugabe is in military custody after an apparent coup d’etat brought an end to his 37-year rule. Meanwhile Zuma is set to be replaced as the leader of the ruling African National Congress next month, and may be forced to step down from his eight-year-old presidency before the end of his term in 2019. On