She does not shirk or play down the consequences of Mobutu's rule or the decline of a prosperous country into bankruptcy. In pitiless detail she recounts how the copper mines and diamond fields were looted, the profits diverted to the private accounts of the president and his cronies. She describes the preposterous palace in the jungle, the houses in France and Switzerland, the chartered Concordes. She conveys all the horrors of an army, overarmed and underpaid, that had gone out of control.

But she keeps asking how it was allowed to happen. She shows how the terrible dictatorship of the Belgian King Leopold, who made the Congo his private colony and massacred and humiliated its inhabitants, provided the prelude to Mobutu's own dictatorship; and how so many others, from dissident politicians to foreign diplomats were willingly conniving in the tyranny.

She shows how cynically Belgian, French and American diplomats competed and conspired to use the deteriorating regime for their own ends, and how Mobutu could manipulate and squeeze them like putty in his hands. 'He played us like a Stradivarius,' said Chester Crocker, in charge of American policy on Africa under Reagan.

The author is most devastating in her condemnation of the World Bank and the IMF (she might have also included several commercial banks) who continued lending without proper safeguards when they already knew that the money was going into Mobutu's coffers. It was a scandalous misuse of international institutions. But talking to officials in Washington, she was surprised by their refusal to recognise their blunders, or take any blame.

They felt a constant pressure to lend to developing countries, however shaky or corrupt; and by the time the debts went bad the official had moved on. Her account of how the IMF helped to ruin the Congo is all the more effective through its quiet understatement. 'The image of the Fund going on bended knees to beg one of the world's most corrupt leaders to take its money is not an attractive one.'

Her account of the many other culprits involved in the Congo does not exonerate Mobutu, but it makes his villainy more credible, explaining how quickly opposition crumbled, and how an intelligent and patriotic young soldier turned into a crazed and isolated despot. 'No man is a caricature, no individual can alone bear responsibility for a nation's collapse,' she says in her introduction. 'The momentum behind Zaire's free-fall was generated not by one man, but thousands of compliant collaborators, at home and abroad.'

This is the most gripping and illuminating book about Africa I have read for years, and it throws its light way beyond the borders of the Congo: not just to the neighbouring countries which are now competing for the spoils from the demoralised country, but to the wider problem of preventing the drift to corruption and tyranny in other parts of Africa.

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