There is some evidence to suggest
that there was a 5th portal associated with the Oil
It would have been added after the complex was built, probably in early 1940,
and was situated on the Fort
Southwick escape tunnel approach road.
That a structure existed here is
beyond doubt, as it is still marked on the most recent (2002) OS
1:25000 maps. A report states that it was of similar construction
to the other Fuel Reservoir access sites; sloping sides leading
downwards to the access door. The spoil heap from the
digging of this portal is also shown the the OS map and was
re-located in June 2002. From here it was possible to move north,
and slightly west to find the structure as marked on the map. All
evidence of this portal has now been erased from the landscape,
and the general area is covered in the most incredibly dense
undergrowth. There is also a foot of dead material laying on the
ground beneath the scrub making any further survey impossible
without better resources.
strongly suspected that later during
World War II the Fuel Bunkers were connected via a tunnel to the UGHQ
under Fort Southwick, and it is assumed that this 5th portal was
part of this new connection.