One man can stop the unnecessary bloodshed in Ukraine. But how can Russian President Vladimir Putin be prevailed upon? Every measure employed so far has failed. Stiff sanctions and warnings by Western and other leaders and the United States-backed Nato alliance have been ignored. Military equipment, worth millions, promised by the US and European nations will help replenish fast-depleting Ukrainian supplies. But the effect could well be to prolong the war. Severe financial and economic sanctions on Mr Putin, members of his inner circle, the Russian central bank and major financial institutions will serve to exclude Russia from the global financial system, tip it into a financial crisis and cripple his ability to finance the war.

These moves may be effective to some extent: the lives of ordinary Russians have already been disrupted, the rouble has crashed, interest rates have doubled overnight and the airspace closed to Russian planes. Mr Putin's government will come under pressure but the sanctions have not been extended to the critical energy sector through which Russia earns billions of dollars from the sale of natural gas to European consumers.