Mersea Fort

Mersea Fort stands on the East Mersea coast in Essex, where the River Colne meets the sea. Built in 1543 under Henry VIII, it was a triangular artillery fort with earthwork walls and three bastions for guns. The fort defended the river’s entrance and worked with nearby blockhouses at St Osyth and Brightlingsea. It was first abandoned in 1552 but returned to service several times, including during the Second English Civil War. By the 18th century, the site had fallen into ruins and was damaged further by a sea wall. The fort’s military role was matched by its importance to the local oyster trade. An admiralty court sat there to enforce fishing rules, showing Colchester’s authority up the estuary. During the Second English Civil War, General Thomas Fairfax seized the fort to cut off supplies to Royalist-held Colchester. The garrison later grew to 36 men, with repairs and new buildings added in the 1650s. After the Civil War, the court moved to Colchester’s Moot Hall, though a yearly ceremony continued at the nearby Mersea Stone. Today, the remains of Mersea Fort are protected as a scheduled monument. Excavations between 2002 and 2003 uncovered timber structures exposed by coastal erosion. The site includes traces of the earthworks, bastions and defensive ditch. Visitors can walk the outlines of the fort and see where guns once stood. The nearby Mersea Stone marks the old court’s annual gathering spot. The landscape still shows how the fort once controlled the river and sea approaches.