Great powers have gathered in Potsdam, Germany. The British are changing prime ministers. The French are annoyed at being excluded. The Poles are worried about being sold out. A great deal rests on the Americans.

But there end the similarities between the Potsdam conference of 1945 that set the new international postwar order and this week’s meeting in the German city of the “Group of Four” – the European Union, the United States, Brazil and India – at the heart of the so-called Doha round of trade talks.