Steamships became ever bigger and the lock soon proved to have been insufficiently enlarged. The South Dock was, excepting Tilbury, the deepest dock in the Port in the late nineteenth century, but access was restricted by the length of its entrance lock. Use of the South Dock fell markedly after the opening of the rebuilt Blackwall entrance in 1894. Its berths were too valuable to be left idle, however, and in 1897 H. F. Donaldson proposed a cut from the Export Dock as a means of reviving it. However, Captain Charles Ayerst, a dockmaster, objected that two berths would be destroyed and that, in any case, the Blackwall entrance was already used to its limit. He suggested the reconstruction of the South Dock entrance, to deepen it and provide a uniform width. Inverted-arched bottoms had become inconvenient because ships of squarish section reduced the effective depth of the lock to that measured at the sides. The question remained unresolved until 1899, when the Joint Committee Chairman, Charles James Cater Scott, intervened decisively in favour of enlarging the lock. Henry Charles Baggallay prepared plans, and Charles Hay Walker & Company, who had recently built docks at Buenos Aires, carried out the work in 1900?2 for £54,833. (fn. 186) The lock was made 29ft deep with a squared concrete bottom, and lengthened from 300ft to 480ft in mass concrete with granite dressings. The lengthening amounted to the addition of an 180ft-long inner chamber in the South Dock Basin, giving long and short locks to permit the locking of small craft without serious water loss, following the examples of the Millwall Dock and Blackwall entrance locks. One of the little-used pairs of gates in the passage between the South Dock and its basin was repositioned. (fn. 187)
