Thames Water Authority is one of the largest water authorities in the world, dealing with water supply and sewage treatment. Besides all the tank and plant accommodation, space was needed for laboratories, cafeterias, offices, changing facilities, various workshops, chemical stores, generators and general stores. Thames Water Authority‘s special knowledge and expertise is commercially available, giving rise to large numbers of visitors who come from all over the world to view the methods and machinery; hence the unusual demand for a visitors‘ centre. The building arrangement combines the visitors‘ centre with the everyday operations of the water treatment plant. Visitors are made to feel that they are at the centre of operations, while operations can be carried out unhindered by their presence.