There are two levels of basement beneath the lower-ground shop floor: the ‘sub’ and the ‘sub-sub’. Combined, these descend below street level. These two areas are then split into two more areas: the dry sub and sub-sub, and their "wet" equivalents. The wet area is beneath the original nine-and-a-half bays closest to the Duke Street corner of the 1909 building. The "dry" is under the rear of the building, known as the SWOD after the surrounding four streets – Somerset, Wigmore, Orchard and Duke – that once enclosed it. During World War II after the entry of the United States into the conflict, from 1942 the dry sub-sub SWOD was used by the United States Army. The building had one of the only secure telex lines, was safe from bombing, and was close to the US Embassy on Grosvenor Square. Initially used by U.S. General Dwight D. Eisenhower, the commander of SHAEF, it later housed 50 soldiers from the 805th Signal Service Company of the US Army Signal Corps, who installed a SIGSALY code-scrambling device connected to a similar terminal in the Pentagon building. The first conference took place on 15 July 1943. Initial visitors included Prime Minister Winston Churchill, to enable secure communications with the President of the United States, although later extensions were installed to both 10 Downing Street and the Cabinet War Rooms. Rumours persist of a tunnel built from Selfridges to the embassy so that personnel could move between the two in safety, with interrogation cells for prisoners hewn from the resultant uneven space available. While restoration work was carried in 2002, the scaffold surround was used to carry the largest photographic artwork ever produced, tall by long and weighing two tons. Created by Sam Taylor-Wood, it showed a gathering of well-known pop and cultural figures of the time, including Sir Elton John. The new store opened to the public on 15 March 1909, employing 1,400 staff, setting new standards for the retailing business. At that time, women were beginning to enjoy the fruits of emancipation by wandering unescorted around London. A canny marketer, Selfridge promoted the radical notion of shopping for pleasure rather than necessity. The store was extensively promoted through paid advertising. The shop floors were structured so that goods could be made more accessible to customers. There were elegant restaurants with modest prices, a library, reading and writing rooms, special reception rooms for French, German, American and "Colonial" customers, a First Aid Room, and a Silence Room, with soft lights, deep chairs, and double-glazing, all intended to keep customers in the store as long as possible.