Low-level exchange rate hostilities with occasional flashpoints have dominated what have become known over the past 18 months as the international “currency wars”. With hot money seeking a safe home, countries can find themselves confronted with a wall of capital and scrambling for tools to prevent their currency appreciating in a way that disrupts local economies.

Whether it is China’s accumulation of thousands of billions of dollars in foreign exchange reserves, Japan’s sporadic interventions on currency markets, the Swiss ceiling on the value of its franc, Brazil’s efforts to tax inflows of capital or the US Senate’s vote to punish Beijing for seeking to hold down the renminbi, the currency wars cast a shadow over the global economy.

If ever there was an area ripe for Group of 20 co-ordination for the good of the global economy it would be currencies, since a depreciation for one is an appreciation for everyone else. Yet so difficult is international discussion of the topic that all that can be agreed are largely meaningless formulations to which everyone is willing to sign up.