| Mersea Fort | |
|---|---|
| East Mersea, Essex, England | |
  Mersea Fort | |
| Coordinates | 51°47′48″N 1°00′12″E / 51.79674°N 1.00343°E |
| Type | Device Fort |
| Site information | |
| Open to the public | Yes |
| Condition | Ruined |
| Site history | |
| Built | 1543 |
| Materials | Earth |
| Events | Second English Civil War |
Mersea Fort, also known as Cudmore Grove Blockhouse, was an artillery fort established by Henry VIII on the East Mersea coast in 1543. It formed part of the King's Device programme to protect against invasion from France and the Holy Roman Empire, and defended the River Colne that led to the town of Colchester. It was triangular in shape, with earthwork walls and three bastions to hold artillery. It was demobilised in 1552, but was brought back into use several times over the next century and saw service during the Second English Civil War of 1648. The fort hosted an admiralty court to oversea the local oyster trade, until the dilapidation of the site forced the court to move to the Moot Hall in Colchester in the middle of the 18th century. A new gun battery was built at the fort during the Napoleonic Wars, but the fortification then fell into decline and was extensively damaged by the construction of a sea wall along the coast. The remains of the earthworks were excavated by archaeologists between 2002 and 2003.