Sheila Dillon goes foraging for wild mushrooms in the Peak District in Derbyshire to find out what common fungi are easy to find - and delicious to eat. She hears from expert foragers, mushroom buyers and fungi fanatics about how the supply chain for this wild food works, from the forest floors of Eastern Europe to China's vast mushroom drying warehouses, as well as the lucrative, and sometimes dubious, trade of some of the most valuable mushrooms.