The African National Congress has dominated South African politics for the last 29 years, but the party of Nelson Mandela is in trouble. A power crisis is doing new damage to an economy already hit by shocking levels of poverty, inequality and corruption. If the ANC is faltering, who stands best placed to offer an alternative? Stephen Sackur speaks to the leader of the radical populist Economic Freedom Fighters, Julius Malema. What will happen to South Africa if he gets even a share of power?