Getting 190 countries to commit to giving up coal has taken years of lobbying and diplomatic lever-pulling by a coalition of countries including the UK and Canada.
It's a big deal.
Coal is by far the biggest source of man-made greenhouse gases.
But to keep global warming below 1.5 degrees, the International Energy Agency has said new investment in all fossil fuel projects has to end this year. That's not just coal, that's oil and natural gas.
This is why the agreement between 20 countries at COP26 to stop lending money to overseas fossil fuel projects, including oil and natural gas, is such an important step.
And it's not a tiny step, either.
Canada, one of the signatories, is the world's largest funder of international oil and gas projects - bigger than China. The US and UK are other major players too.
What's more, the deal has taken just six months to negotiate, and since the 20 countries came forward at COP26, it is understood that two others - Germany and France - are thinking of joining them. And the 20 states, and a few of their development banks, have agreed to stop funding by 2022.
Could this be the moment the tide turns not just against coal, but all fossil fuels? Maybe, but there is a long way to go.
The fossil fuel phase-out only applies to overseas projects, so that would allow the UK government to continue supporting oil exploration in the North Sea.
Canada and the US can still exploit their own vast oil and gas reserves.
And like most of the announcements so far at this summit, this is a political agreement. No country is bound by any of the pledges they commit to outside the Paris climate process.
But the direction of travel seems clear, with fossil fuels in the rearview mirror. It's just hard to tell how quickly they'll fade into the distance.
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