Dartmouth Castle is one of a pair of forts, the other being Kingswear Castle, that guard the mouth of the Dart Estuary in Devon, England (). A small fortalice (coastal fort) was built in 1388 under the direction of John Hawley (rumoured to be the basis for the Shipman in Chaucer's Canterbury Tales). The present Guntower building is the earliest surviving English coastal fortress specifically built to carry guns. It was built by the corporation of Dartmouth between 1481 and 1495 and additions, including open-air gun platforms, were made during the 16th century by Henry VIII and again in the 17th century in order to accommodate new military technology.