Gordon Brown did something curious in his rapturously received speech before a joint session of the US Congress on Wednesday morning. After flattering Americans with references to their daring and initiative, after congratulating them as visionaries who made the impossible possible, the British prime minister felt the need to embolden them to fight the present credit crisis. “There is no financial orthodoxy so entrenched, there is no conventional thinking so ingrained, there is no special interest so strong,” he said, “that it should ever stand in the way of the change that hard-working families now need.”

But the orthodoxies and conventions Mr Brown is questioning are those of his opponents. The most concrete and impassioned part of his speech involved the defence of an orthodoxy of his own – free trade. “Today’s financial institutions,” Mr Brown said, “are so interwoven that a bad bank anywhere is a threat to good banks everywhere.” After thus laying out neatly the rationale on which tariff barriers were erected in the 1930s, he warned against repeating the mistake, against succumbing “to a race to the bottom and a protectionism that in the end protects no one”. This is probably still good advice. But the awkwardness with which it was proffered shows that the financial crisis – and especially the reaction of the US and UK governments – has robbed the case for free trade of some of its internal logic.