of General Hugh Debbrieg, chief engineer for Lord Amherst. Debbrieg had originally helped in the "Cumberland Lines" planning with Capt. Desmaretze. His plan for the Chatham lines, drawn by Joseph Heath and dated 1755, is kept at the British Museum. Also in 1802–11, prisoners, mostly convicts from St Mary's Island, were set to work on extending the tunnels and creating vast underground stores and shelters, new magazines, barracks, gun batteries and guardrooms. More than 50 smooth-bore cannon were also mounted. The last building works were completed in about 1820. A maze of tunnels, used to move ammunition around the fort, were dug into the chalk cliffs. A second gun battery, 'Townsend Redoubt', was built at the northeastern corner of the dockyard at the same time as Fort Amherst. Both forts were inside the 1756 brick-lined earthwork bastions known as the "Cumberland Lines", which surrounded the whole east side of the dockyard down to St Mary's Island. These have now been built over. Fort Clarence in Rochester and Fort Pitt, on the Rochester-Chatham borders, were built in 1805–15 to protect the southern approaches. Although the Lines were never put to the test, their design would have made a formidable defence against any invasion force. In 1820, because of improvements in artillery equipment and greater firing ranges, the defences were declared obsolete. The entire fortified area was then used as a training-ground during the Victorian era, with practice sieges becoming so popular that they attracted thousands of visitors to Chatham. VIPs were seated on the Casemated Barracks that once stood in the Lower Lines and also on Prince William's Barracks within Fort Amherst itself. One such siege is described in Charles Dickens Pickwick Papers. Fort Amherst has been described by English Heritage as the most complete Napoleonic fortification in Britain and as such has great national historical significance. In 1959, the site was scheduled as an ancient monument. The fort was still in use during the Second World War when it served as an Air Raid Warning command post. It later underwent restoration to make more areas accessible to the public. An attempt was made by the Royal Engineers, to convert the Fort into a display ground for their military vehicles, as an offshoot of the Royal Engineers Museum in Gillingham, but this was prevented by a lack of finance. Current use In the late 1970s a group of enthusiasts were given