This would be a poor decision, a strategic solution to a financial problem. Yes, Rio needs money quickly. But institutional investors are in a forgiving mood. Xstrata proved as much with a cheeky cash call last month. Fresh equity capital for Rio, combined with frozen or scrapped dividends and capital spending pared to a minimum, could tide over the world's fourth-largest materials company, without it needing handouts from one ranked 23rd.

A company that overpaid for Alcan, in cash, at the top of the cycle, is now praying it can sell well at the bottom. Given its desperation, heightened by the embarrassing loss of incoming chairman Jim Leng, that may be a tall order. For 136 years, Rio has directed its own destiny. Now, under chief executive Tom Albanese and outgoing chairman Paul Skinner, it is poised to allow into the boardroom and various operating businesses not just a key customer, but also a state-controlled firm with an interest in low prices for high grade iron ore.

A deal in which shareholders sacrifice not just upside as and when the commodities cycle turns, but also a future takeover premium would have little appeal. Shareholders must look hard at the terms. If they offer less value, they must instead demand the rights issue Mr Leng so wanted. Mr Albanese's position, already weak, would then be untenable. And the BP nominations committee would have to reflect hard on whether Mr Skinner, for all his valuable experience at Shell and sharp business brain, was still the best person to chair its board.