Portsdown Underground Fuel Bunker By Bob Hunt


The Portsdown Underground Fuel Bunker was built during the late 1930s and early 1940s, by Sir Robert McAlpine’s construction company, as a bombproof Royal Navy fuel oil reservoir to serve the fleet at the Portsmouth Naval Base. The oil was needed as a guaranteed supply for Royal Navy warships in case oil deliveries to western British seaports were blockaded by the German Navy (a typical underhand Nazi trick).  Three were built in the UK the others being at Inchindown some 4 miles to the north of the then naval base at Invergordon and Lyness at the Scapa Flow Naval Base, but the one under Portsdown is one of the largest and best preserved remaining examples. I contacted McAlpines but no records of the construction of the Fuel Bunker exist anymore. In fact very little information exists anywhere. It is my belief that the Portsdown Fuel Bunker had a special purpose and was not just constructed to supply the Royal Navy with fuel during wartime. I think a secondary aim was to ensure an absolutely uninterruptible supply of fuel oil for the D-day invasion fleet of 6 June 1944 and I have shown some evidence of this later on. Other invasion support services like communications and logistics certainly took a very robust approach to their roles, as failure of the landings was unthinkable, but one thing was certain: lack of marine fuel was never going to be a problem.

The cover story put out during the construction of the Fuel Bunker was that they were prospecting for oil. This was not so far from the truth. During March 1936 the tranquillity of Portsdown was shattered by the installation of an oil drilling rig by the D’Arcy Exploration Company, a subsidiary of the Anglo-Iranian Oil Company. During the drilling of the test bore a small mining village temporarily sprang up on the hillside.


Portsdown Hill Oil Drilling


The 136 feet (41 metres) derrick drilled to a depth of one mile (1.6 km) but oil in commercial quantities was not found. The site was abandoned on 17 February, 1938. Attempts have recently been made to reactivate the licence for this site and look for oil using modern methods.

The Fuel Bunker had an official capacity of 135,000 tons ­(137,700 tonnes) of furnace fuel oil (FFO), which was the main warship fuel of World War Two. FFO is a ‘residual’ fuel: it’s what you are left with once all other products, such as petrol and diesel, have been distilled from crude oil. It is a filthy, treacle-like substance, and it was cheap.

The whole complex, which is 120 feet (37 metres) underground, consists of 2 miles (3.2 kms) of tunnelling and contains nine 40 feet (11 metres) high, concrete storage tanks. There is also a large underground pumping station containing 2 pre-war pumps which were used to pump the fuel to, and from, the Oil Fuel Jetty in Portsmouth Harbour, 6 miles (9.6 km) away.


pump room


The pipeline consisted of two 16 inch (41 cm) FFO pipes, and one 10 inch (25 cm) diesel pipe which ran from Portsdown through Portchester, Fareham Creek, Fleetlands, Frater, Priddy’s Hard, Forton Lake and terminated at the Forton Oil Fuel Depot, Gosport.   

The walls of the bunkers are made of concrete 1 foot (30 cm) thick, and in places the roof is 22 feet (6.7 metres) thick; no German bomb produced during WWII was capable of this level of penetration. 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 workings; the priest seemed to be on constant call. There is a tale of two Irish workers who took a nap behind some shuttering after having a drop of Guinness during their lunch break. Forty tons (41 tonnes) of wet concrete were inadvertently poured on them and even to this day they still form part of the tunnel lining.

Due to the end of the Cold War and the fact that the fleet now operates on F76 diesel fuel, the pipeline and Fuel Bunker were decommissioned during the early 1990s, and the booster pumping station at Bedenham Lane in Gosport was demolished. The pumping station at the Forton Oil Fuel Depot is still intact and has been saved from demolition. Some of the last ships to use FFO were the Leander class frigates, the Falklands veteran aircraft carrier HMS Hermes, and the Royal Yacht Britannia. 


oil fuel map 1

Plan 01. A plan of the entire Fuel Bunker including the surface features.

The Fuel Cells are numbered 1 to 9

AWestern Pipe Tunnel Portal
BEastern Access Portal
CPipe Tunnel
DAccess Tunnel
EB2177 Road
FPumping Chamber
GMachinery Shaft and Standby Generator
HStaircase to Surface Exit
JWest Cell Access Tunnel
KNorthern Tunnel
LNorthern Portal
MEast Cell Access Tunnel

doors open west tunnel

fuel bunker northside closeup

pipe tunnel south looing to north portal 2150 feet long

The Pipeline

The buried pipeline from the Fuel Bunker ran south for 6 miles (9.6 km) to the fuel oil depot at Forton, Gosport. Initially I believed the pipeline would emerge out of the Fuel Bunker and run south under the sea across Portsmouth Harbour to the fuel depot as this seemed to be by far the easiest and least expensive method. However, this is not the case because in the 1930s underwater pipeline technology was relatively primitive and corrosion of the steel pipe work was very hard to control. Consequently with the exception of two short underwater sections most of the pipeline runs underground and consists of 1 x 10 inch (25 cm) pipe for diesel and 2 x 16 inch (40 cm) pipes for FFO.

When the pipeline was laid most of the area around the Fuel Bunker was farmland and the M27 Motorway was most definitely not there! After WWII, as the area around the pipeline was built on, a 15 foot (4.5 metres) wide strip of ground above it was fenced off using 4 foot (1.2 metre) concrete posts and chain link fencing. By 2005 most of the evidence of the pipelines above- ground existence had disappeared with the exception of a 1970s built inspection pit, one sign and odds and ends of fencing. The residents of the area had been offered the chance to buy the pipeline land if it ran next to their property and most of them did so. This land is now classified as ‘contaminated’ and cannot be built on.

There were twenty one inspection pits situated at regular intervals along the pipeline containing isolation and diversion valves. Nearer to the Fuel Bunker the pipeline plans show that ‘special air pits’ were installed. I assume these were used to bleed the air out of the pipeline when fuel was being pumped uphill to the bunkers.  At the Inchindown Fuel Depot along the pipeline to Invergordon electrical fuel heaters were installed every 200 yards (182 metres) to make the fuel oil less viscous (more runny). This was not the case at Portsdown possibly due to the milder southern climate but mainly because only light viscosity 50/50 FFO was stored at Portsdown which does not need heating to make it pumpable.  The FFO inside the cells of the Fuel Bunker was not heated either: the brute force of six large pumps was all that was needed to shift it.

oil fuel map 2

Plan 02. This traces the route of the pipeline from Portsdown to Forton.

Gosport Oil Fuel Depot

Extracted from my unpublished book: The Portsdown Fuel Bunker.

Copyright Robert Hunt – 2015