Johannesburg

The man who fervently believes in his destiny to lead South Africa had sex with an HIV-positive woman less than half his age who had been raped in her early life.

Let that sentence sink in as you consider the behaviour of Jacob Zuma, once deputy president of Africa's political and economic powerhouse and still arguably its most popular active politician.

Mr Zuma is now on trial accused of raping the 31-year-old woman who had known him since childhood and called him "uncle". In some countries, this kind of thing might damage a politician's popular standing, especially as Mr Zuma faces another trial on two counts of alleged corruption.

But not here. Instead, the affable Zulu politician is cheered to the echo whenever he appears in public. Mr Zuma's performances before the rank and file of the ruling ANC are a sight to behold.

Traditional praise-singers, clad in leopardskin headdresses, open proceedings by hailing his innumerable virtues. Then Mr Zuma usually leads the crowd in singing a lively ditty of his own composition called Bring Me My Machine Gun.

He concludes with a trademark dance - again of his own invention - involving arm movements suggesting that he is alternately drying his back with a towel and pointing out a distant aircraft.

First things first. Mr Zuma pleads innocent on all charges. He denies raping the woman. He denies being corrupt. And the crowds do not cheer because they approve of rape and corruption.

They believe Mr Zuma to be a "man of the people" and the innocent victim of a vast conspiracy masterminded by his boss, Thabo Mbeki, designed to thwart his destiny as South Africa's next leader.

So far, Mr Zuma has not given evidence in his own defence in the trial before Johannesburg's High Court. Let us presume him innocent of rape, and stick to the accepted facts.

Mr Zuma, 63, has not denied having sex with the woman - a long-standing family friend and prominent anti-Aids campaigner - when she stayed at his Johannesburg home on November 2 last year. He is expected to plead that the encounter was consensual.

Never mind that he has two wives, as well as one divorced wife, one deceased wife and 10 children - some of them younger than the woman he slept with. What must be explained is why Mr Zuma chose to have sex with a woman who became HIV-positive when she was raped in her early life.

Nothing I have read in any South African newspaper has addressed this question. We have been regaled with salacious details of exactly how the encounter allegedly took place - one newspaper helpfully provided a cartoon of the scene that had Mr Zuma pictured in bed with the woman and, as she asks what he is doing and why the bed is shaking, he replies that an "earthquake" is taking place *1.

But no one has examined the possible explanations for why Mr Zuma, who wants to be president and presumably values his life, would have sex with someone who is HIV-positive.

There are not many theories that make any sense. Does he perhaps agree with the HIV/Aids denialists - with whom Mr Mbeki famously flirted - who hold that the epidemic is a myth invented by Western drug companies to peddle their products on hapless Africans?

If you think it implausible for a senior African politician to believe this, consider the Nobel Peace prize-winner and Kenyan minister Wangari Maathai, who thinks that Aids was invented by unnamed Western scientists as a "weapon of mass destruction" for use "against blacks".

Or did Mr Zuma have protected sex? We do not know whether a condom was used in the encounter. Even if it was, the protection offered is not 100 per cent and there is still a strong element of recklessness. Or is Mr Zuma among the 16 per cent of adult South Africans who are HIV-positive?

We have no idea. And South Africa's media have carefully steered clear of these questions. Pending the outcome of the court cases, we must assume that Mr Zuma's behaviour was not criminal. But it was certainly reckless. Although he was sacked as deputy president last June, "Msholozi", as Mr Zuma is popularly known, remains the ANC's deputy leader.

He still believes in his destiny. Only last weekend, he told a rally that he was resisting the temptation to form his own party and would "solve" his problems within the ANC. Mr Zuma thus served notice that he intends to remain a thorn in Mr Mbeki's side. So the burning question still demands an answer from this man who aspires to lead his nation - what on earth did you think you were doing?

With acknowledgements to David Blair and Telegraph UK.