 Callender's Cable & Construction Company was founded by William Ormiston Callender in 1870.It was originally an importer and refiner of bitumen for road construction but began manufacturing insulated cables at their Erith site on the Thames in the 1880s.It played a significant role in construction of the British National Grid in the 1930s building the 132 kV crossing of the Thames at Dagenham with overhead cables spanning 3060 feet (932m) between two 487 ft (148m) towers, and allowing 250 ft (76m) clearance for shipping.