The Portsmouth Block Mills form part of the Portsmouth Dockyard at Portsmouth, Hampshire, England, and were built during the Napoleonic Wars to supply the British Royal Navy with pulley blocks. They started the age of mass-production using all-metal machine tools and are regarded as one of the seminal buildings of the British Industrial Revolution. They are also the site of the first stationary steam engines used by the Admiralty. Since 2003 English Heritage has been undertaking a detailed survey of the buildings and the records relating to the machines. Development of Portsmouth Dockyard The Royal Navy had evolved with Britain's development by the middle of the eighteenth century into what has been described as the greatest industrial power in the western world. The Admiralty and Navy Board began a programme of modernisation of dockyards at Portsmouth and Plymouth such that by the start of the war with Revolutionary France they possessed the most up-to-date fleet facilities in Europe. The dock system at Portsmouth has its origins in the work of Edmund Dummer in the 1690s. He constructed a series of basins and wet and dry docks. Alterations were made to these in the course of the eighteenth century. One of the basins had become redundant by 1770 and it was proposed to use this as a sump into which all the water from the other facilities could drain. The water was pumped out by a series of horse-operated chain pumps. In 1795, Brigadier-General Sir Samuel Bentham was appointed by the Admiralty, the first (and only) Inspector General of Naval Works with the task of continuing this modernisation, and in particular the introduction of steam power and mechanising the production processes in the dockyard. His office employed several specialists as his assistants — mechanists (engineers), draughtsmen, architects, chemists, clerks, and others. The Inspector General's office was responsible for the introduction at Portsmouth of a plant for the rolling of copper plates for sheathing ship's hulls and for forging-mills for the production of metal parts used in the construction of vessels. They also introduced similar modernisation at the other Naval dockyards in conjunction with M I Brunel and Maudslay. By 1797 work had started on building additional dry docks and on deepening the basins, and Bentham realised that the existing drainage system would not cope with the increased demand. He installed a steam engine designed by a member of his staff, James