Coalhouse Fort is an artillery fort built in the 1860s to guard the lower Thames from seaborne attack. It stands at Coalhouse Point in Essex on the north bank of the river, at a location that was vulnerable to raiders and invaders. It was the last in a series of fortifications dating back to the 15th century and was the direct successor to a smaller mid-19th century fort built on the same site. Constructed during a period of tension with France, its location on marshy ground caused problems from the start and led to a lengthy construction process. The fort was equipped with a variety of large-calibre artillery guns and the most modern defensive facilities at the time, including shell-proof casemates protected by granite facing and cast-iron shields. However, its lengthy construction and th