Stand on the riverside path at Kingswear and look across the narrow throat of the Dart estuary. Two stone towers face each other across roughly 300 yards of tidal water - Dartmouth Castle on the far side, Kingswear Castle on this one. In the 1490s, when Henry VII still ruled England and Columbus had just sailed, the men of Dartmouth built these towers to do something specific that almost no one in Britain had built a fort to do yet: hold gunpowder cannon at sea level and fire them directly at the waterline of any French ship that tried to come up the river. The English had been fighting France for most of a century. The harbour they were protecting was rich. So they built one of the very first purpose-built artillery forts in Britain - and then it sat here, mostly quiet, for the next five hundred years.
Dartmouth's harbour in the 15th century could hold up to 600 vessels. It was one of the great ports of southern England, a base for trade, fishing, and the wine ships that came up from Bordeaux. Wealth attracted enemies. France was always a threat across the Channel, and the town had already invested in walls and chains to close the river mouth. Between 1486 and 1495 Dartmouth turned its older castle on the west side of the estuary into a true artillery fort. But cannon need to come from both sides if they are to catch a ship in crossfire. So in 1491 work began on a matching tower on the east bank, on the rocks below the village of Kingswear. By 1502 it was finished: a square, three-storey block of slate rubble with red sandstone trim, large rectangular gun-ports cut close to the waterline on the ground floor, more guns and a garrison room above. The two castles together could close the river to anything that floated.
The castle had its busy moment in the English Civil War. In 1642 Dartmouth and Kingswear took the Parliament side, and the town spent money strengthening Kingswear's doors. A year later Prince Maurice, the Royalist commander, besieged and took Dartmouth, and Kingswear with it. The Royalists threw up an earthwork called Mount Ridley behind the castle to cover its vulnerable landward side. In January 1646 Sir Thomas Fairfax brought a Parliamentary army down through south Devon, recaptured Dartmouth in a tight, professional operation, and took Kingswear back from Sir Henry Cary, the High Sheriff of Devon, who had been left to defend it. Sir Henry was heavily fined by Parliament. By 1661, when Charles II had been restored to the throne, the castle's roof had been burnt off during the fighting and replaced in lead. Guns were mounted up there too, looking out over the river. It was the only time in five centuries the building ever actually mattered in a war.
By the early 18th century the range of naval artillery had outgrown the castle. Ships could now stand off and out-shoot anything mounted in a fixed tower at sea level. Kingswear Castle still had 12-pounder, 9-pounder, and 8-pounder guns installed as late as 1717, but its real life as a fort was over. The roof leaked, the floors rotted, ivy climbed the walls. In 1855 a Victorian gentleman named Charles Seale-Hayne restored it as a summer house - a private retreat with the most photogenic view in Devon, where you could drink tea in a room with gun-ports for windows. During the Second World War the Royal Marines briefly camped here and added a concrete blockhouse, the kind of squat ugly thing that 1940 produced everywhere along the south coast. After the war the castle returned to private hands. Today the Landmark Trust manages it as a holiday let. You can rent the whole tower, sleep in the room that once held the garrison, and watch the river traffic pass beneath you exactly where the Tudor cannons used to point.
Coordinates 50.342 N, 3.560 W. Kingswear Castle sits on the east bank of the River Dart at the river's mouth, with Dartmouth Castle on the opposite shore about 300 yards west. Best viewed at 1,500-2,500 ft AGL - the two castles bracket the river entrance and make a memorable visual pair. Exeter (EGTE) is 25 nm to the north-northeast; the south Devon coast runs east toward Brixham and west toward Salcombe. The Dart estuary is one of the most photographed harbours in southern England.