An article in the Guardian details the unexpected challenge by shareholder-activists to the ethics of some of the holdings of Berkshire Hathaway, run by the widely admired American financier Warren Buffett.

The challenge was over Berkshire Hathaway’s investment in a subsidiary of the Chinese state oil company CNPC; CNPC itself was alleged by activists to be implicated in channelling funds to the Sudanese military, and therefore by extension in Darfur. What’s interesting is that the increased scrutiny of Buffett’s holdings has followed his decision last year to donate $31 billion to the Gates Foundation to support its work in developing countries.

But – according to the Guardian – “a recent investigation by the Los Angeles Times concluded that 87% of Berkshire investments were in companies facing allegations of environmental irresponsibility, human rights violations and other activities contrary to the [Gates] foundation’s values.”

Perhaps not surprising – given Berkshire Hathaway’s huge rate of growth over the last 40 years, Buffett’s modest lifestyle and customary humility not withstanding.