 The line to be followed by these entrenchments was supported by thirteen permanent small polygonal forts or redoubts called London Mobilisation Centres, which were equipped with all the stores and ammunition that would be needed by the troops tasked with digging and manning the positions.The 1859 Royal Commission on the Defence of the United Kingdom report on Britain's defences believed that London was practically undefendable; they proposed a fort at Shooters Hill to defend the Royal Arsenal at Woolwich, but it was never acted upon.Following a number of proposals by senior military figures, an 1888 memorandum written by Colonel John Charles Ardagh envisaged a scheme of simple earthworks for infantry and moveable armaments, intended to be dug and manned in an emergency by the Volunteer Force, the line being supported by permanent works, the London Mobilisation Centres, at 5 mile (8 km) intervals, which acted as stores and magazines.