His voice shaking, Thabo Mbeki bid farewell to the presidency and the people of South Africa on Sunday, saying thank you in eight of the country's official languages. A personal tragedy for the President, it may prove a momentous turning point, Shakespearean in its grand political drama and flawed personalities.

Coriolanus - the Roman general too proud to beg for votes from the common people - is said to be Mr Mbeki's favourite play, but Friday's meeting of the African National Congress (ANC) leadership was more like Julius Caesar. It was Mr Mbeki's Ides of March as, one after another, “comrades” - as they still like to refer to each other - plunged their knives in. If nothing else, the unseemly haste of this political murder shows the depth of his unpopularity and the bitterness of the enemies he has sidelined.

The opportunity was presented by a judge, Chris Nicholson, who ruled last week that Jacob Zuma, president of the ANC and president-in-waiting of the country, had been victim of a political plot by Mr Mbeki. The case concerned corruption in a 1999 arms deal in which some $200 million was allegedly paid to the ANC and individuals including Mr Zuma.

Mr Mbeki will be replaced on Thursday by Kgalema Motlanthe, the deputy president of the ANC, who will serve as caretaker until the election next year. This will give time for Mr Zuma, elected party president in December, to become an MP and, after the party-based election due in April, to be elected by Parliament as national president. If all goes to plan. But Judge Nicholson called for a full inquiry into the arms deal. Its revelations might prevent Mr Zuma from running for president. It will also lead to British Aerospace, one of the arms sellers. Britain is directly involved in this drama.

When Mr Mbeki took over in 1999 South Africa had enjoyed five years of Nelson Mandela's benign rule. A graduate of Sussex University, Mr Mbeki was assumed to have solid leftist beliefs. But he immediately embarked on a strongly pro-business economic strategy and promoted Black Economic Empowerment, making companies give a proportion of shares as well as jobs to black South Africans. This has created a wealthy black elite and helped the economy to grow at more than 5 per cent for the past five years.

Although an intellectual, Mr Mbeki has always been quirky, picking over truths that others take for granted and aggressive in defence of his own theories. Experience of racism in Britain as well as South Africa may have been formative and his views were often based on race rather than class. Mr Mbeki's defence of his bizarre refusal to acknowledge the link between HIV and Aids was often accompanied by attacks on white perceptions of black sexuality, delivered with venom. He saw at the heart of the Aids debate a conspiracy of white drug companies and hinted that antiretroviral drugs were poisoning Africans. On Zimbabwe I often had the impression that he would not have defended Robert Mugabe so diligently had Mr Mugabe not been attacked so vehemently by Britain and America.

On a more positive side he promoted a continent-wide African Renaissance to build an Africa proud of its heritage, doing much to build the African Union out of the useless Organisation of African Unity and to establish the principles of the New Partnership for Africa's Development, a deal between African states and their partners.

He was brought down not by ideology but by his own arrogance in alienating so many colleagues. Although he created several black millionaires and perhaps assumed that they would keep control of the ANC, he excluded the trade union movement and the Communist Party, which represent the majority have-nots. They took over the ANC at the grass roots. When the lights went out in January because the Government failed to notice rising demand for electricity and stagnant supply, he also lost his reputation as a manager.

Mr Zuma could not be more different. A man of great charm and quick intelligence, if he feels disadvantaged by having had little formal education he does not show it. While Mr Mbeki led the diplomatic wing of the ANC in exile in the 1980s, Mr Zuma rose to be head of intelligence. The movement was constantly under threat from the apartheid Government's spies and assassins. Several leading ANC members were murdered, others were turned by bribes. Trained by the Russians and the East German Stasi secret police, the ANC dealt ruthlessly with suspects. Mr Zuma knows where the bodies are buried.

A great public speaker, he can talk to ordinary black South Africans in a way that Mr Mbeki never could. But he gives in to the temptation to tell people what they want to hear. South Africa is still living out its bad history and its peoples have so many competing interests that only a magician could keep them all happy.

Mr Zuma's strongest supporters are militants in the union movement and the party. They control many local party branches and it will be impossible to ignore them. But he will have to balance demands for more state spending and job creation, with the demands of business for continued freedom to make money and move it in and out of the country. If he ignores these, South Africa, with its severe current account deficit, will suffer massive capital flight. If he continues Mr Mbeki's pro-business agenda his supporters will ditch him.

The next few months will be an extraordinary test for South Africa's institutions; the party itself, the courts and parliament. They are still strong despite the country's propensity for living on the edge. No other country in Africa could have removed its president in such a way by legal and democratic means.

Richard Dowden is director of the Royal African Society. His book Africa: Altered States, Ordinary Miracles is published by Portobello Books

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