Defending Britain’s Soft Underbelly: Invasion, Fortification and Geology Near Portsmouth, Hampshire

Abstract

The artillery forts along the English Channel owe their origins to Pleistocene megafloods that drowned the river valleys feeding into the pre-Pleistocene Channel River. The Channel coast consists mainly of cliffs, so only these deep-water estuaries could be used for invasions. The most important fortified area was Portsmouth in Hampshire where the coastline consists of spits, beaches, lagoons, marshes and islands. The bedrock is Eocene sands and clays that form terraces. Cretaceous chalk is located behind and above the terraces. This paper addresses artillery forts built as a result of invasion threats during the reign of Henry VIII and in the mid-Victorian period. The Henrician forts are located on the shingle spits and beaches and the Palmerston forts, on higher-ground surrounding Portsmouth. The Henrician forts are low, stone-built structures constructed for coastal defence; the Palmerston forts were built of brick and soil to defend against land attack. These differences mainly reflect the fast-developing advances in artillery technology and naval tactics that began in the 1840s. The Henrician forts were decommissioned in the mid-twentieth century, but some of the Palmerston forts live on and have been retained in military ownership into the current century, but not as artillery forts.

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