Just over three years ago, the UN launched its Sustainable Development Goals to push world leaders into addressing problems such as poverty, hunger and climate change by 2030.

It sounded admirable, and these days those SDGs have become a useful framework for discussing global development. They have also spawned an eye-catching rainbow lapel pin that government officials and business leaders often wear as a virtue-signalling device. “The SDGs are a great road map,” enthuses Paul Polman, former Unilever chief executive.

But there is one gigantic catch: money. Since the SDGs were launched, the World Bank has estimated that it will take about $4tn of annual investment to create the infrastructure needed to achieve the goals. Various UN bodies put the price tag at between $5tn and $7tn each year.