The financial crisis is shaking up the commodities market. But while the focus so far has been on falling prices, the critical impact is centred in the market’s plumbing: the over-the-counter deals, where companies, investors and banks trade in private, bilateral contracts.

The crisis is generating a double problem. The collapse of banks such as Lehman Brothers has elevated counterparty risk as market participants fear that the other side of their deals could default on its obligations.