The story of Uralkali and Belaruskali would make a fine Ian Fleming novel. Russian and Belarusian potash miners clash, wrecking their lucrative marketing cartel. The chief executive of Uralkali, the Russian miner, is arrested in Belarus while on his way to meet the Belarusian prime minister. Russian oligarchs come under political pressure to sell their big stakes in Uralkali. And now: enter China. A unit of China’s sovereign wealth fund exchanged its Uralkali bonds for a 12.5 per cent equity stake yesterday. Is its play political, economic, or both?

Uralkali is the world’s largest producer of potash, a material used to make fertiliser. China, its biggest client, making up about a third of its sales in volume terms, has much to gain from low fertiliser prices. That makes Uralkali, as the lowest-cost potash producer, a good choice. It can extract a tonne of the stuff for $62 – half the level of, say, Canadian rival PotashCorp – and deliver it to China for under $150. So Uralkali will remain profitable even if the price falls hard from its current $440 a tonne. Just as well: since the collapse of its arrangement with Belaruskali in July, Uralkali has focused on volume over price.

But there are a lot of unknowns. Uralkali’s boss is still behind bars in Belarus. Uralkali’s biggest shareholder, Suleiman Kerimov – who sold the bonds to China Investment Corporation last year – is in talks to sell his remaining 22 per cent stake, possibly to buyers close to the Russian state. Further Russian political influence over Uralkali could limit CIC’s ability to shape the miner’s strategy. And the marketing cartel could still be revived. If that happens, and the potash price rises, it would probably increase the value of CIC’s investment, at least in the near term – but China’s strategic interests would suffer.