The Mulberry harbours were two temporary portable harbours developed by the British Admiralty and War Office during the Second World War to facilitate the rapid offloading of cargo onto beaches during the Allied invasion of Normandy in June 1944. They were designed in 1942, then built in under a year in great secrecy; within hours of the Allies creating beachheads after D-Day, sections of the two prefabricated harbours were towed across the English Channel from southern England and placed in position off Omaha Beach and Gold Beach, along with old ships to be sunk as breakwaters.