A fortress, called Sheppey Castle or Queenborough Castle, was built to guard the passage of ships along the Swale upon the command of King Edward III between 1361–1377, during the Hundred Years' War with France. It was built on the site of a much earlier, but smaller castle. Its unusual design – round and symmetrical – was described by historians Howard Colvin and R. Allen Brown as "exemplifying the principles of cylindrical and concentric fortification carried to their logical conclusion with perfect symmetry". They also suggest that the design, which bore similarities to Henry VIII's Device Forts of the 16th century, may have been designed to defend against and to make best use of gunpowder artillery. Queenborough was the only true concentric castle built in England. It regained importance in the 16th century under Thomas Cheney, when it is thought to have influenced the construction of nearby Deal Castle and Walmer Castle.