With the approach of war in the 1930s, the Admiralty built protected storage for fuel at a number of ports. In Dover’s case, in 1939 five tanks were built by Lindsay Parkinson and Company in the cliffs behind the docks. Access was from two parallel tunnels, each penetrating around 250 metres. Between these access routes, the five tanks were each 600 feet (180 metres) long, 9.9 metres wide and 12.2 metres tall.
The capacity of each tunnel was an impresssive 19 million litres (c4.1 million gallons). Four of the tanks held furnace fuel oil and the fifth held diesel. The tanks were constructed at a higher level than the docks so that ships could be fed by gravity in the event of a power failure. Post World WarrII, Esso took over the tanks before they were decommissioned in the 1960s.