The London docks have a water area of over 723 acres, with 33 miles of quays, very extensive warehouse accommodation, and dry-docking advantages of the highest standard. All the main-line railways have access to the London docks, and it is here that much of their freight business arises. London heads the list of British ports, alike from the point of view of the value of its import and export trade, the volume of shipping using its facilities, and the amount of tonnage registered. For the year 1928 the value of London's imports and exports was £692,730,351. Liverpool coming second with £485,386,171, and Hull, Manchester, Southampton and Glasgow following in the order named. The most important dock works completed in London since the Great War are the King George V. dock, with an entrance lock 800 feet long, forming with the Victoria and Albert docks a water area of 245 acres, the largest single sheet of dock water in the world; the modernisation of the West India and Millwall docks; and the extensive additions made to the shipping accommodation at Tilbury, which include a new dry dock 750 feet in length and a commodious new landing stage for passengers.