From the National Heritage List for England: Details: The monument includes a martello tower set within a dry moat and with an outer glacis (sloping bank), and supporting the remains of a later, World War II observation post. The tower is situated on Radnor Cliff and overlooks a residential area below and the coastline beyond. It is the most easterly in a cliff top series of six moated towers, constructed in 1805-6 to guard the coastline between Hythe and Folkestone, and lies around 400m south east of its neighbouring tower, no 5. The slightly elliptical, brick built tower measures up to around 13m in diameter externally and stands complete to its original height of about 10m. The upper half of the tower protrudes above the lip of the brick built retaining wall of the moat, which encircles the base at a distance of around 10m and was intended to provide further protection from both cannon fire and ground assault. As part of the original design, soil was built up against the outer face of the moat wall to form a glacis, which slopes away from the lip of the moat for a distance of around 10m. The glacis has been disturbed along its north eastern edge by the construction of a modern house, and has been partly destroyed by the construction of a modern road along its southern edge. The tower was constructed on three levels, with battered (inwardly sloping) walls, designed to deflect cannon shot, ranging from 1.6m to around 4m in thickness, the most substantial section being the wall base on the southerly, seaward side. The external face of the walls was rendered in a cement mortar, or stucco, which served to strengthen the outer skin of bricks. A thick central column rises from the basement to the top of the tower, from which springs the barrel vaulted first floor ceiling which supports the gun platform on the roof. Access into the tower is by way of a first floor doorway, which was originally approached by a drawbridge across the moat, capable of being raised to seal the entrance. The bridge no longer survives, although part of the mechanism used to raise it remains within the tower, above the entrance door. The first floor was divided into three rooms by wooden partitions, which do not survive, and provided accommodation for the garrison of 24 men and one officer. Two fireplaces heated the rooms, which were lit by two windows, one of which was enlarged to form a door when the tower was reused during World War II, and the jambs of the second window were cut back to form splays. The openings are headed by air vents. The brick lined basement is reached by a trap door leading down through the suspended timber floor near the entrance. This was used to store ammunition and supplies, and provision for these includes a vaulted gunpowder store, or magazine, partly recessed into the thickness of the outer wall. The eastern partition wall of the magazine was subsequently removed, and two further walls added, during a later phase of refurbishment. Safety features included lantern windows in the partition walls, separated from the magazine by panes of glass. Ammunition lift shafts, linking the gun emplacement to the basement level, were also inserted within the thickness of the wall at a later date. Cisterns dug into the basement floor, fed by rainwater pipes leading down from the roof, were designed to augment the water supply, and a slate water tank, subsequently installed beneath the floor, still survives. The open gun platform is reached from the first floor by an internal stone staircase constructed in the thickest part of the tower wall. The original wooden door from the head of the staircase remains on the roof. The circular roof space, designed to accommodate a 24-pounder cannon mounted on a wooden traversing carriage, retains most of its original features, including the raised central pedestal which supported the gun pivot, and the raised perimeter step, with both inner and outer iron gun rails surviving intact. The operation of the cannon, which had a range of around 1.5km and could be turned through 360 degrees by a series of rope pulleys, required 10 to 14 men. The six iron hauling rings used for traversing and preparing the cannon, survive in the parapet wall which encircles the roof. Four ammunition stores, in the form of arched recesses, and a smaller niche, thought to have housed a gunpowder flask, are also set into the parapet wall. The smaller recess was altered when the adjacent lift shaft was installed. Superimposed onto the original roof features are the remains of a World War II observation post comprising a series of brick walls surviving to a height of around 1m. All modern fences, the modern pond and its stone surround; the stone revetment along the north eastern edge of the glacis, and all other modern fixtures and fittings are excluded from the scheduling, although the ground beneath these features is included. Reasons for Designation: Martello towers are gun towers constructed to defend the vulnerable south eastern coast of England against the threat of ship-borne invasion by Napoleonic forces. Built as a systematic chain of defence in two phases, between 1805-1810 along the coasts of East Sussex and Kent, and between 1808- 1812 along the coasts of Essex and Suffolk, the design of martello towers was based on a fortified tower at Mortella Point in Corsica which had put up a prolonged resistance to British forces in 1793. The towers take the form of compact, free-standing circular buildings on three levels built of rendered brick. The towers of the south coast were numbered 1-74 from east to west, while those of the east coast were identified by a system of letters (A-Z, and then AA-CC) from south to north. Although they exhibit a marked uniformity of design, minor variations are discernible between the southern and eastern groups and amongst individual towers, due mainly to the practice of entrusting their construction to local sub-contractors. Most southern towers are elliptical in plan, whilst the eastern group are oval or cam-shaped externally, with axes at the base ranging between 14.4m by 13.5m and 16.9m by 17.7m. All are circular internally, the battered (inwardly sloping) walls of varying thicknesses, but with the thickest section invariably facing the seaward side. Most stand to a height of around 10m. Many martello towers are surrounded by dry moats originally encircled by counterscarp banks, and/or have cunettes (narrower water defences) situated at the foot of the tower wall. The ground floor was used for storage, with accommodation for the garrison provided on the first floor, and the main gun platform on the roof. The southern towers carried a single 24 pounder cannon, whilst the eastern line carried three guns (usually a 24 pounder cannon and two shorter guns or howitzers). Three large, circular ten- gun towers known as redoubts were also constructed at particularly vulnerable points, at Dymchurch, Eastbourne and Harwich. All three survive. As the expected Napoleonic invasion attempt did not materialise, the defensive strength of the martello tower system was never tested, and the tower design was soon rendered obsolete by new developments in heavy artillery. Many were abandoned and fell into decay or were demolished during the 19th century, although some continued in use into the 20th century as signalling or coastguard stations and a few saw use as look out points or gun emplacements during the two World Wars. Of the original 74 towers on the south coast, 26 now survive, and of the 29 on the east coast, 17 now survive. Those which survive well and display a diversity of original components are considered to merit protection. Martello tower no 4 at Cliff Road, Folkestone, survives well despite some later alterations, and retains a substantial proportion of its original components and associated features, including the glacis bank. It serves as a valued local landmark and, when viewed as one of a series of six cliff top towers, no 4 illustrates the strategically planned integration of the martello tower system. The construction of an observation post on the roof of the tower during World War II, demonstrates the continued significance of this location and provides an insight into the role of coastal defence during the 19th and early 20th centuries.