Martello Towers are a distinctive feature of the coasts of South-East England, and there are several well-preserved examples in Suffolk, like this one at Felixstowe Ferry. They were built as a defence against invasion by Napoleon in the first decade of the 19th century. No radar then, or reconnaissance aircraft, just a small army troop with brass telescopes in a Martello Tower. Built with thick stone walls to withstand naval cannon fire, they had their own cannon on the flat, wide roof, and the circular shape and location on an empty shore gave the garrison 360 degree surveillance. I like to imagine a motley Georgian Dad’s Army squad living in, and drilling around, the tower, preparing earnestly for the invasion that never came. Nowadays their use varies from private houses and holiday homes to museums and galleries.