London Stock Exchange mining giants ENRC and Glencore have some questions to answer about the company they keep in Africa. This week, no less an organisation than the International Monetary Fund cast an extraordinary level of doubt over the two companies' main fixer in the Congo – the colourful Israeli diamond merchant Dan Gertler.
Regular readers of the Independent may recall how ENRC bought mining assets illegally expropriated by the Congolese government from another London-listed firm, First Quantum.
The middleman in this deal was the billionaire Gertler, a close friend and sometime bankroller of president Joseph Kabila's government. The ENRC deal became famous because the company ended up having to pay First Quantum more than $1bn in compensation.
Mr Gertler's name appears on countless controversial mining sales in the country. Time and again, the Kabila government has sold him mining rights for an allegedly knockdown price, and he has then sold them on at a huge profit – several to ENRC, others to Glencore, the corporate octopus of the minerals mining, transporting and trading world.
He denies he pays below market prices, but companies affiliated to him in at least three cases paid below the valuations made by analysts at Deutsche Bank, Numis Securities and Oriel Securities, Bloomberg reported this week.
According to the Global Witness non-governmental organisation, the money Mr Gertler receives from his deals invariably goes into his offshore companies, the beneficiaries of which, he says, are his family trust.
Opposition leaders have attacked Mr Kabila and his government repeatedly for not holding proper open tenders for mineral resources. With such opacity, it is hard to verify Mr Gertler's claim that he received no preferential price.
The 38-year-old Mr Gertler, like ENRC and Glencore, claims his work in Congo helps bring in western investment to a country in desperate need of financial help. He points to his own philanthropy there, even declaring to Bloomberg this week: "I should get a Nobel prize".
But of course every dollar Mr Kabila's regime allegedly discounts from the possible market price of Congo's minerals when it sells them to him is a dollar not going to the Congolese people.
This week, the IMF decided enough was enough. Having been lobbied for months, if not years, by big western investors about the malodorous way Congo's mineral wealth was being sold off by Kabila, the IMF froze a $532m loan programme to the country.
Hundreds of millions of dollars of international aid that should be helping the world's most deprived nation are being put on hold because of the deals surrounding ENRC and Glencore's best chums in Africa. Surely this should make us in Britain feel uncomfortable, at least. Other aid programmes to the Congo could also be reviewed as a result of the IMF's decision. The UK is due to give £900 million of aid to Congo in the next five years.
The IMF specifically cited the way Mr Kabila's government had failed to publish full and transparent details on how it sold to a Gertler company a stake in a mine it ran with ENRC. When it gave Kabila one last chance to publish a clear explanation of how the ENRC mine deal worked, he failed to deliver, putting out instead an incomplete picture of the transactions.
In the words of the IMF's man in Congo, Oscar Melhado: "IMF staff consider that the information contained in the published note falls short of the requirement for extending the [loan] agreement."
Mr Kabila is a questionable character at best. He has faced allegations – which he denies – that he rigged the 2011 election. Global Witness says there is a serious risk the mining deals could be lining the pockets of corrupt officials. But when western mining firms are prepared to tolerate the Congolese way of doing business, surely they only deepen the problem.
Willy Vangu, a Congolese opposition leader working as professor of nuclear medicine in Johannesburg, thinks so. He has been instrumental in pushing for the IMF loan to be frozen due to the alleged corruption in the sale of minerals rights, visiting London earlier this year to lobby British MPs.
"Nobody wants to see the IMF money not going to the people of Congo," he says from his university office in South Africa, "But let's be honest here, a $523 million loan agreement is nothing compared to the amount of money that is escaping Congo's mines. About $5.5 billion has been taken from the country in the past five or six years from these deals. If Congo was managed properly, we would not need the IMF."
ENRC has stated it is committed to upholding the highest standards of corporate governance, while Glencore says it takes care to act in line with its corporate practice principles and laws including the UK Bribery Act.
Mr Kabila is under huge pressure in Eastern Congo from the M23 rebel group. He will, in all likelihood, hold on to power, mixing and blending new alliances and compromise deals with the various factions, as he has throughout his reign – it's a skill that's earned him the nickname 'The Maker of Omelettes'.
But Mr Vangu has a message that ENRC, Glencore and other western firms should heed. "Kabila will not last for ever. It may take six months, it may take five years. But when we take over, we will certainly look to renegotiate these mining contracts. We want to create a win-win, where these western companies get to make a profit and the Congolese people share. We do not want a tangle in the mud with these companies. But if they are not prepared to co-operate, we will have no choice but to seize the assets. And if they are unhappy with that, they can take the country to the international courts."
I wonder: would ENRC and Glencore really want to see their deals with Mr Gertler picked apart in an open court?