Some barricade the entrances to their fields with concrete blocks and fallen trees.

The prince’s warning comes as wildfires rage in parts of Europe and the UK during a spell of extreme heat.

Thomas Cazenave says they are preparing if further evacuations are issued, as the mayor of a nearby town called the situation “catastrophic”.

Certain types of severe wildfire can create pyrocumulonimbus – something that Nasa calls the “fire-breathing dragon of clouds”.

Astronomers warn it would tear the heart out of UK science, and leave a generation untrained.

Blazes are about 15km from Bordeaux, but the city’s mayor says there are no plans to evacuate.