Legends & Mysteries

Hillsley Road

 Created 02-04-2003   Last update 02-04-2005

click the arrow


page 2 of 3


rear of Hillsley Road

The back of the houses in Hillsley Road, looking north west. To the left of the path on the lower left is the M27 Motorway cutting (out of shot). The building which replaced the subsided buildings is arrowed. On the top right are the spoil heaps from the UGHQ under Fort Southwick.

Hillsley Road

Looking west along Hillsley Road. The arrowed building replaced the one that subsided. At the very end of the road - which is a cul-de-sac - are the southern portals of the Naval Fuel Bunkers.

Aerial view of the Hillsley Road area

An aerial view of Hillsley Road showing the relationship of the Fuel Bunkers, the UGHQ under Fort Southwick and the M27 Motorway.


A The 2 southern portals of the Fuel Bunkers. These both lead north to just beyond the B2177
B B2177 - James Callagan Drive
C The northern Fuel Bunker portal
D The area above the Fuel Bunkers proper
E Fort Southwick
F The furthest south the UGHQ tunnels go under the Fort
G Hillsley Road
H The M27 south coast Motorway

Analysis of the known facts

The cause of the problems affecting Hillsley Road could be attributable to any or a combination of the following:

  • the underground Fuel Bunkers

  • the UGHQ under Fort Southwick

  • the construction of the M27 Motorway 

  • an unrecognised underground system, including collapsed pipes

  • a natural fault in the underlying chalk

These will now be examined one by one.

Fuel Bunkers

The two southern portals of the Fuel Bunkers are located at the western end of Hillsley Road, and from these long access tunnels run north into the hillside. The actual fuel bunkers themselves are located to the north of the B2177, which is the road which runs west / east along the top of Portsdown Hill. Click here for the bunker plan. This means that the Fuel Bunker underground complex is 400  yards to the northwest of Hillsley Road, and is also on a much higher elevation. 


Fort Southwick UGHQ

Fort Southwick is located on top of Portsdown Hill to the north of Hillsley Road. Underneath the Fort is a Underground Headquarters (UGHQ) built during WWII. Most of the UGHQ runs to the south of the Fort, but even so the closest the underground complex gets to Hillsley Road is 200 yards. Also the UGHQ tunnels are at least 100 feet higher in elevation. 


M27 Motorway

This was constructed during the early 1970s although the route for it was planned as far back as 1947. It runs parallel to Hillsley Road in a massive cutting just yards to the south - see the top photo and the map  above. The excavation of the cutting was necessary to keep the gradient of the new road within motorway tolerances, and due to its proximity to Hillsley Road it could have been a factor in the problems experienced there. However this factor has been the subject of a survey and has apparently been ruled out, and even though it could explain the subsidence it would not explain the strange noises coming from under the ground. 


An unrecognised underground system

There has been much speculation about an undisclosed, underground Cold War related complex, such as a nuclear shelter for Portsmouth's elite and an underground barracks for NBC clad defence troops. Although the Fuel Bunkers and the UGHQ mentioned above are substantial works - at least 3 miles of tunnel between them - I can say with confidence that they are the only major underground features in this area. It would just not be possible to excavate and then conceal a new underground work without evidence of its existence becoming available. Besides if the Motorway cutting was planned in 1947 then tunnelling work in the area would have been avoided. There is however a possible exception to this which is dealt with on page 3.

A collapsed pipeline from the Fuel Bunker has been cited as a possible cause, and some residents noted a 'fuel oil' smell in their homes. The route of this pipeline which runs from the Bunker across Portsmouth Harbour and then onto Gosport is not precisely known, but there no reason why it should run east along Hillsley Road when Gosport is to the south. It is also difficult to see how a collapse of this nature could have caused such havoc - and what about the noises?


Natural ground fault

This would initially seem to be a reasonable explanation for subsidence, but the chalk under Portsdown is around 400 feet deep, and you could expect any ground faults to be revealed during the house building phase. It is also quite rare for building subsidence to occur on chalk.  It is possible that the construction of the M27 Motorway triggered unrest in an already weak area of ground. The dates would be favourable for this idea: the Motorway was built in the early 1970s, and the problems were reported in the 1980s and 90s. However this once again leaves us without an explanation for the underground noises.


The list of possible causes described above seems exhaustive, and yet no single cause will explain the three problems experienced in Hillsley Road, which are:

  • subsidence of buildings, pavements and lamposts

  • noises emanating from the ground which sound like human activity  

  • fuel oil smells

It seems then that we are dealing with a combination of causes, so let's deal with each problem in turn. 



The Fuel Bunker complex and the UGHQ as they were originally built can be ruled out, and it looks very unlikely that they were enlarged in later years in the direction of Hillsley Road because:

  • it was known in 1947 that a Motorway would one day pass through this area so further underground work there should have been avoided

  • any expansion of the existing underground systems would surly have taken place in a west to east direction to ensure that there was sufficient depth of ground above the tunnels and to keep them level. If additional tunnels were made southwards towards Hillsley Road then the tunnels would either run downwards at a gradient of 30 degrees, or a vertical shaft of 100 feet would be required to get under the road - what would be the point in this? 

The construction of the M27 Motorway has got to be a prime contender for the subsidence found at Hillsley Road. Although a survey was made to determine if this was responsible it is has never been made public, and all the properties affected were owned by Portsmouth City Council, so the matter was never pursued. If you take a look at the photo at the top of this page you will see that the properties in the road are about 75 feet away from the Motorway cutting, and if the ground in parts was already naturally weak then this could have provoked the subsidence. No other parts of the housing estate have been affected by subsidence, which would tend to rule out a ground fault being responsible on its own.

An undisclosed underground system seems more unlikely now than it did when first suggested in the 1980s. This type of subterranea would have been Cold War related, and with this era long gone evidence of its existence would have come to light - it hasn't. As described above this area does not lend itself to underground works, especially secret ones - it is populated, too far down Portsdown Hill, has poor access, and had roadway development pending. 


Underground Noises

These have been described as: heavy machinery operating, metallic sounds, and tapping. All of these would have been generated by the daily routine in the Fuel Bunkers when they were operational. The only other underground location was the UGHQ, and this had long since been abandoned. However there is an anomaly here which is detailed on page 3

Although much has been made in this account of the distance between the Fuel Bunkers and the affected properties, the sounds could have been carried by any of the usual underground services: water, gas, power, comms and sewage systems, most of which would have had a direct connection with the Fuel Bunkers. 

Another possibility is that certain geologies, especially  fissures, can act as good conductors of sound, so that noises can be heard some way from its source, particularly if the sound is of a subterranean origin. Such similar phenomena have been experienced in the Coalfields in the north of England in the past.


Fuel Oil Smells

 First on the list must be the Fuel Bunkers. With nine 50 year old reservoirs holding thousands of tons of Fuel Furnace Oil it would not be unreasonable to expect the occasional or even permanent leak. The containment of lost oil was provided for as the Bunkers were equipped with emergency soak-aways, and since these were higher than Hillsley Road the oil would have gravitated to that area.

The smell could also have come from the M27 Motorway, as the prevailing southwesterly winds would have carried the Motorway fumes directly over Hillsley Road.


Here we had an underground complex of 2 miles of tunnel containing thousands of tons of fuel oil, big pumps to move it around and active maintenance crews. Is it any wonder then that residents heard noises and smelt oil fumes? The reason why blame was never attributed to the Fuel Bunkers is because they never existed - not officially anyway. This was a common phenomenon of WWII and the Cold War: such sites weren't just secret and not to be talked about, officially they never existed and consequently were always blameless!


click the arrow


page 2 of 3