Crown Prince Mohammed bin Salman of Saudi Arabia, who has not till now shown any great enthusiasm for tackling climate chaos, is working on designs for an environmentally-friendly new city in the kingdom.

At successive international climate meetings Saudi Arabia, the world’s biggest oil exporter, has been among those states which have obstructed rather than encouraged attempts to tackle the increasingly urgent problems associated with a fast-warming world.

But recently Prince Mohammed, seen very much as the power behind the Saudi throne, has been talking of building a zero emissions city and establishing what he describes as “a blueprint for how people and planet can co-exist in harmony.”