“Portsdown hill fuel depot were built during the late 1930s as bombproof Naval Oil Reservoirs. I believe that three of this type were built in UK. During the 1990s the extensive undergrowth was cleared away, the perimeter fence was replaced, and the site including the pipeline was decommissioned. This corresponds to the closure of other Royal Naval underground storage facilities such as the Invergordon oil depot, Copenacre, Hartham Park and Monk’s Park. The site is listed in the MOD National Asset Register as the Portsdown Oil Fuel Depot. In the past, residents in the surrounding area have complained of strange underground noises.
The underground chamber contains nine 35 feet high concrete storage tanks, most of which are capable of holding 19,500 tons of Furnace Fuel Oil. There is also a large pumping station containing 2 pre-war pumps which were used to pump the oil to the oil fuel jetty in Portsmouth Harbour. The walls of the reservoir were made of concrete 22 feet thick, and no bomb produced during WWII was capable of penetrating this structure. At least 15 men died during the construction, usually due to rock falls. Many of the construction workers were Irish Catholics, and the last rites were frequently given inside the cavern; the priest seemed to be on constant call.
The oil was needed as an emergency supply for British warships in case oil deliveries to western British ports were blockaded by the German Navy. The construction work was undertaken by Sir Robert McAlpine’s construction company.”
Thanks to Mark Twiglet fro 28DL for the pics