Details

The monument, which includes a World War II Heavy Anti-aircraft (HAA)
gunsite and its associated ancillary buildings, is situated at Monument
Farm and protected in three separate areas. The gunsite, known as Nelson
or P12 (Portsmouth 12), formed part of a chain of batteries positioned to
defend the industrial and military targets of Portsmouth and Southampton.
It is situated on the crest of a hill with views to Portsmouth,
Southampton and the hinterland and lies about 700m north west of Fort
Nelson, which was one of the key ammunition depots for anti-aircraft
deployment in the area.
Sources indicate that the gunsite was well established by 1941 and
equipped with four 3.7 inch guns and a GL Mk II radar by 1942. As part of
a larger building programme initiated at the onset of the Blitz, the
construction of four 5.25 inch gun emplacements at Monument Farm began in
April 1944 with an expected completion date of February 1945. In January
1946 the battery was selected to form part of the reduced, post-War layout
known as the Nucleus Force, and served as a Nucleus Force Battery
Headquarters with its guns permanently mounted.
The earlier installation consists of a north west facing semicircular
arrangement of four octagonal 3.7 inch gun emplacements, surrounding a
central command post. The command post was mounded over after the war, but
survives as a a largely buried feature with its roof just emerging.
Whereas the guns' concrete holdfasts survive with many of the securing
bolts still in place, the surrounding blast walls and ammunition lockers
have been removed.
A second construction phase began in 1944, when four 5.25 inch gun
emplacements facing south west were built around the western part of the
3.7 inch gun formation. These brick and concrete gunpits and adjoining
machinery rooms are mostly heavily overgrown but well preserved. The three
levels, on which the gunpits operated, remain intact. At the central level
are the holdfasts with their emerging securing bolts, surrounded by the
spent cartridge trenches and upper tiers, where the crew was positioned.
The gunners had access to 14 lockers in the ammunition gallery, which also
acted as a blast wall. Stairs give access to the partially sunken machinery
rooms, some of which are fitted with the original doors. The northernmost
emplacement was infilled but survives as a buried feature.
The emplacements were served by several storage magazines, such as a
Nissen hut about 60m east of the central control building. Its original
red brick walls survive, as does a blast wall, covering its northern
aspect. Another 30m east of the Nissen hut is a flat-roofed single storey
engine room with a large ventilation window surviving at the back of the
building.
Approximately 150m south of the gun emplacements are two small buildings,
which are thought to have been contemporary with the 3.7 inch gunsite and
used for the storage of radar equipment. The southernmost is a single
storey flat-roofed concrete structure, which is now completely overgrown.
Its larger north western neighbour is made of brick on a concrete base,
and was encased within a new wall and roof after the site's Cold War
phase.
A second control building was established probably contemporarily with the
5.25 inch gun emplacements. It lies 200m east of the first control
building and is well preserved. It consists of a flat-roofed single storey
structure with its main entrance on the north, while two staircases on the
south acted as emergency exits. On the western wall a ventilation shaft is
visible. About 30m to the north west is a small flat-roofed concrete
switch gear shed.
The battery is reached from the main gate at Swivelton Lane, via a concrete
service road which loops around the central command post with offshoots
leading to each of the 5.25 inch gun positions.
The domestic camp lies east of the gun emplacements, but is not included
in the scheduling as none of the original buildings survive.
The following items are excluded from the scheduling: the later barns
constructed beside the Nissen hut and against the engine room; all later
surfaces, fences, gates and structures; and all later materials and
equipment stored within and around the emplacements. However, the ground
beneath all these features is included.

MAP EXTRACT
The site of the monument is shown on the attached map extract.
It includes a 2 metre boundary around the archaeological features,
considered to be essential for the monument's support and preservation.

Source: Historic England

Reasons for Scheduling

Although of comparatively recent date, 20th century military sites are
increasingly seen as historic survivals representing a defining episode in the
history of warfare and of the century in general; as such they merit careful
record and, in some cases, preservation. One of the more significant
developments in the evolution of warfare during this period was the emergence
of strategic bombing in World War II, and this significance was reflected by
the resources invested in defence, both in terms of personnel and the sites on
which they served. During the war, the number of people in Anti-aircraft
Command reached a peak of 274,900 men, additional to the women soldiers of the
ATS who served on gunsites from summer 1941, and the Home Guard who manned
many sites later in the war. A national survey of England's Anti-aircraft
provision, based on archive sources, has produced a detailed record of how
many sites there were, where they were and what they looked like. It is also
now known from a survey of aerial photographs how many of these survive.
Anti-aircraft gunsites divide into three main types: those for heavy guns
(HAA), light guns (LAA) and batteries for firing primitive unguided rockets
(so called ZAA sites). In addition to gunsites, decoy targets were employed to
deceive enemy bombers, while fighter command played a complementary and
significant role. Following the end of World War II, 192 HAA sites were
selected for post-war use as the Nucleus Force, which was finally closed in
1955.
The HAA sites contained big guns with the function of engaging high flying
strategic bombers, hence their location around the south and east coasts, and
close to large cities and industrial and military targets. Of all the
gunsites, these were the most substantially built. There were three main
types: those for static guns (mostly 4.5 and 3.7 inch); those for 3.7 inch
mobile guns; and sites accommodating 5.25 inch weapons. These were all
distinct in fabric, though they could all occupy the same position at
different dates, or simultaneously by accretion. As well as the four or eight
gun emplacements, with their holdfast mountings for the guns, components will
generally include operational buildings such as a command post, radar
structures including the radar platform, on-site magazines for storing reserve
ammunition, gun stores and generating huts, usually one of the standard Nissen
hut designs. Domestic sites were also a feature of HAA gunsites, with huts,
ablutions blocks, offices, stores and amenities drawn from a common pool of
approved structures. Sites were often also provided with structures for their
close defence; pillboxes are the most common survivals, though earthwork
emplacements were also present. The layout of HAA gunsites was distinctive,
but changed over time, for example to accommodate the introduction of radar
from December 1940, women soldiers from summer 1941, and eight gun layouts
from late 1942.
Nearly 1,000 gunsites were built during World War II, and less than 200 of
these have some remains surviving. However, at only around 60 sites are these
remains thought sufficient to provide an understanding of their original form
and function. This includes 30 of the 192 examples which continued in use
until 1955. Surviving examples are therefore sufficiently rare to suggest that
all 60 well preserved examples are of national importance.

The World War II Heavy Anti-aircraft gunsite (P12) at Monument Farm is well
preserved and will contain a wealth of archaeological evidence relating to
the construction and usage of the site. The surviving remains represent at
least two stages of development (early World War II and late World War II),
and provide a rare insight into the development of Heavy Anti-aircraft
batteries. The site is close to Fort Nelson, providing a unique picture of
the organisation of defence on the south coast.

Source: Historic England