The Islip Reserve Fuel Depot was built for the R.A.F.prior to World War II for airfield fuel supply and later taken over by ESSO. GPSS stands for Government Pipelines & Storage System. The depot was first used in the late 1930s by the RAF as a reserve fuel depot with a capacity of around 6500 tons. After the war the site was taken over by Esso as a fuel dispersal depot, and it was expanded in the 1960's. The site closed down in 1969. It is believed it was used after 1969 to supply jet fuel to RAF Upper Heyford as the pipeline stretched out to a village next to the airbase. The pumps have been disused since the early 1990's, and the base closed down in 1994.