The atrocities now being committed daily in Zimbabwe have reached a bestial nadir. Those daring to challenge Robert Mugabe are beaten and killed. Their wives are mutilated and burnt alive in their homes. Their villages are denied food and their families starved into submission. The bravery and tenacity, nevertheless, of Morgan Tsvangirai and fellow opposition supporters is extraordinary and heartening.

What is appalling, however, is that as Zimbabwe disintegrates, the country that could have done much to halt the brutalities and avert the chaos stands by in shameful silence. South Africa's failure to curb Mr Mugabe's excesses is a terrible indictment of its leadership. But it is also a warning. South Africa itself is in trouble. The powerhouse of Africa is running out of power.

Fourteen years after the end of apartheid, such a judgment might seem harsh. The country has avoided a race war. Its growth rate in recent years has been an impressive 5 per cent. Tourism is holding up, as are exports. The country has won global sporting renown and been rewarded with its selection as the venue of the next World Cup in 2010. But even as the stadium girders go up and concrete is poured for a high-speed rail link (see page 47), fears are growing within the country and outside that the showcase event will be overwhelmed by the violence, political tensions and infrastructure failures that point to alarming social, economic and political breakdown.

The economic figures are bleak. Unemployment is running officially at 25 per cent; a more realistic assessment is 44 per cent. The income gap has, if anything, widened since the end of apartheid as a new black middle class has turned its back on the poor: 10 per cent of the population earn more than 50 per cent of the income. Food price inflation jumped to 15 per cent three months ago, petrol prices have risen 33 per cent in a year and South Africa remains acutely vulnerable to these global price rises. Despite welfare grants to 12.5 million people, poverty is growing; violent crime rates, including murder and rape, remain among the world's highest; and a savage new xenophobia has unleashed urban violence on many of the five million immigrants, including around three million Zimbabweans. The infrastructure is creaking, the health service has almost collapsed and power shortages have led to blackouts, with devastating consequences on vital mining industries.

Global confidence is falling. Foreign investment dropped £190 million in the fourth quarter of 2007. Nervous bankers give warnings of deadlock with a lame-duck President Mbeki and a hostile putative successor, Jacob Zuma, who, if he escapes new prosecution charges, may move to economic populism and undo Mr Mbeki's one solid legacy of business-orientated growth policies.

Mr Mbeki has only himself to blame for the deepening pessimism. His aloofness and refusal to accept a third candidate led to the ANC's reckless endorsement of Mr Zuma. His bizarre policies on Aids, misguided reward of political loyalty above government competence, tolerance of corruption and myopia over Zimbabwe have weakened South Africa and lowered its global standing. The economy may muddle through. But now, more than ever, the continent needs confident, cohesive and clear leadership in southern Africa. There is little sign of this in Pretoria.