The conditional agreement to hold oil production steady announced by Saudi Arabia and Russia on Tuesday was a triumph of the art of diplomacy, delivering the maximum rhetorical impact for the minimum genuine commitment. Its careful construction tells you everything you need to know about today’s oil market.

Co-ordinating oil producers to manipulate prices has never been easy, and has been effective only for limited periods, most spectacularly in the 1970s. Since the emergence of US shale oil in the past seven years, it has become just about impossible.

The semi-tough position agreed by Saudi Arabia and Russia may not amount to very much. Oil prices fell sharply in the aftermath of the announcement, although they later rebounded. But in the circumstances, it was the best both countries could have done.