Bank of China and its fellow state-controlled Chinese financial institutions are used to being the piggy banks for pet political projects and China’s spectacular railroad expansion plan certainly falls into that category.

But just because investing in railways is seen by bankers as something of a political task doesn’t mean they are throwing their money away.

More reason for Beijing to wait and see on its exchange rate. The turmoil in global markets last week is likely to have already given Beijing plenty of pause for thought and now the modest trade surplus in April announced today also gives the Chinese government a stronger hand to resist pressure to appreciate.

The trade figures for last month did not, as some economists, predicted, repeat March’s surprise deficit, which had been the first in six years, but in the grand scheme of Chinese trade performance in recent years, the $1.7bn surplus was relatively small. It means, for instance, that over the last three months, China has recorded a trade surplus of only $2bn. Not exactly an obvious sign of a currency that is significantly undervalued.