Alan Yentob joins the South African artist William Kentridge as he prepares an epic frieze along the banks of the River Tiber in Rome. Alan visits him in his hometown of Johannesburg, the inspiration for the magical hand-drawn animated films he calls 'drawings for projection'. Brought up under apartheid, Kentridge has witnessed the fragile transition to a multi-racial democracy, and his art continues to reflect South Africa's turbulent times.