Hidden away deep in the Surrey countryside sits a piece of iconic British history. A structure that Defence Infrastructure Organisation (DIO) proudly cares for and that helped the Allies prepare for the D-Day landings in 1944. The original Atlantic Wall was a series of armouries, bunkers and both natural and man-made obstacles put into place to defend Nazi-occupied Western Europe from an anticipated Allied invasion. Stretching from northern Norway down to the border of France and Spain, the 2,687km wall provided what was thought to be an impenetrable defence for Nazi-occupied Europe. However, on 6 June 1944 as part of meticulously planned Operation Overlord, better known as D-Day, the wall was breached within hours. The Allied success of breaking through the Atlantic Wall came after months of planning and training exercises, including on the replica Atlantic wall in Hankley Common.