Opec's failure to agree a curb on oil production is hardly surprising

It was always unlikely that Iran, newly back in the market, would be able to secure a deal with its big rival Saudi Arabia and others including Russia

Opec struggles to speak with a single voice these days, so it was always a wobbly assumption that the cartel of oil producers would be able to agree a deal with non-members, such as Russia, to curb output.

So it has proved. The weekend talks in Doha fell apart over a single issue. Saudi Arabia wanted Iran, its big regional rival, to be included in a deal to freeze production at January levels. Iran, freshly returned to international markets after the lifting of sanctions, wasn't interested. Its priority is revenues, at almost any oil price, and recovery of lost market share.