Until recently, anyone advocating a global tax on financial transactions was dismissed as hopelessly naive. That was until the world banking system came close to collapse.

While the economies of rich nations dived, those of developing countries foundered. This led to an urgent initiative by the United Nations to find financial mechanisms to protect poor nations.

Exactly 12 months ago, the UN stumbled on one that could be worth at least £40bn. A presentation by David Hillman, the coordinator of a little-known NGO called Stamp Out Poverty, at a high level conference in Doha proved to be pivotal.

With the UN warming to a 0.005% micro tax on currency trading, it gave intellectual credibility to the so-called Leading Group of Nations, a 55-strong body of countries whose task was to find innovative financial answers to poverty. It took the idea to the G20 at Pittsburgh in September.

Meanwhile, German NGOs persuaded Chancellor Angela Merkel and her political rival Peer Steinbrück to back the tax during the German federal election campaign in September.

At the same time, in Pittsburgh, G20 world leaders asked the International Monetary Fund to consider introducing what is widely known as the Tobin tax after the late US Nobel prizewinning economist who dreamed up the device.

When Gordon Brown became the first G20 leader to publicly back the plan, the Tobin tax suddenly shook off its left-field image and crossed over into the political mainstream.

Now that the EU has called on the IMF to back it, its chances of being adopted have remarkably become closer still.