Whilst this was going on, we learnt how to make a sour-dough starter. Once industrial society breaks down, you won't be able to find yeast in the baking section anymore. Sourdough is the answer: it’s basically flour and water, mixed together and left open to the air, and natural yeast in the air that’s fallen in. In effect, this means every sourdough starter is completely determined by its environment.
As long as you keep feeding them, starters last for years. People get quite attached (Jess’ starter is called Maddie). One participant told us about a bakery in France whose starter is 100 years old.
You can find a recipe here.