Wall writes in detail about the different Celtic tribes, whom the Romans thought ‘war mad’, as indeed they doubtless needed to be. He also relates how the landscape of Britain was changed by such activity with castles being built looking out to sea, souterrains or underground tunnels for storage constructed, especially in Cornwall, and large-scale forest clearance undertaken as a result of the need for building hill forts and with early industrialization, such as smelting iron in large quantities.