Reasons for Designation
Since 1916 the Porton Down Range has been used for military purposes. As on
the Salisbury Plain Training Area, this has meant that it has not been subject
to the intensive arable farming seen elsewhere on the Wessex chalk. Porton, as
a result, is one of very few surviving areas of uncultivated chalk downland in
England and contains a range of well-preserved archaeological sites, many of
Neolithic or Bronze Age date. These include long and round barrows, flint
mines, and evidence for settlement, land division and agriculture.
The barrows on Idmiston Down are of bell and bowl form. Bell barrows, the most
visually impressive form of round barrow, are funerary monuments dating to the
Early and Middle Bronze Age, with most examples dating to the period 1500 BC
to 1100 BC. They occur either in isolation or in round barrow cemeteries and
were constructed as single or multiple mounds covering burials, often in pits
and surrounded by an enclosure ditch. The burials are frequently accompanied
by weapons, personal ornaments and pottery and appear to be those of
aristocratic individuals, usually men. Bell barrows are rare nationally, with
less than 250 examples, most of which are in Wessex. Their richness in terms
of grave goods provides evidence for chronological and cultural links amongst
prehistoric communities over most of southern and eastern England. As a
particularly rare form of round barrow, all identified bell barrows would
normally be considered to be of national importance.
Bowl barrows are the most numerous form of round barrow with over 10,000
recorded nationally (many more have already been destroyed), occuring over
most of lowland Britain. They are funerary monuments dating from the Late
Neolithic period to the Late Bronze Age, with most examples belonging to the
period 2400-1500BC. Bowl barrows were constructed as mounds of earth or
rubble, sometimes with a surrounding ditch, and which covered single or
multiple burials. They occur either in isolation or, as with this monument,
associated with barrows of differing type. Often occupying prominent
locations, they are a major historic element in the modern landscape and a
substantial proportion of surviving examples are considered worthy of
Despite limited antiquarian excavation and the subsequent disturbance of the
bell barrow, the barrows on Idmiston Down are comparatively well preserved
examples of their respective classes and will provide evidence of funerary
practices which may span several centuries within the Early Bronze Age. Their
construction and use provides information concerning the diversity of beliefs
and social organisation amongst early prehistoric communities while their
structure will preserve evidence of both past environment and economy.
The gas testing trenches are a rare survival of a class of monument built and
used during the period 1916-1918 which saw the first German use of gas in
warfare and the rapid development of both an offensive and defensive response.
Despite being largely infilled, the majority of the overall layout of the
trenches can still be recognised on the ground. In addition, the buried
features will preserve details of trench construction, use and modification.
The monument includes a bell barrow, three bowl barrows and World War I gas
testing trenches lying at the base of a wide combe on Idmiston Down. The
Bronze Age barrows form the eastern part of a cemetery of eight barrows,
aligned broadly east-west. All four barrows within this monument survive as
recognisable earthworks, the bell barrow and the two larger bowl barrows lying
in an east-west line, with a smaller bowl barrow immediately to the north.
The most westerly bowl barrow has a mound 34m in diameter and 1.5m high, the
profile of which is slightly eccentric. The mound is surrounded by a ditch
which, where undisturbed, is 3m wide and 0.5m deep. On the northern and
western sides of the barrow traces of a low bank, c.3m wide, lie beyond the
ditch. Immediately to the east lies a further bowl barrow which has a flat
topped mound 26m in diameter and 1.8m high. This is surrounded by a ditch 3m
wide and 0.4m deep. The bell barrow which lies to the east of these two bowl
barrows has a mound 23m in diameter and a sloping berm 7m wide. Beyond this
lies a ditch 4m wide and a maximum of 0.6m deep. The north easterly side of
this barrow has, in the past, been considerably disturbed by buildings which
have now been removed and the profile of the mound reinstated. Concrete
foundations still remain on the summit of the mound and spoil tipped down the
south eastern flank of the barrow blurs elements of its profile. To the north
of the three larger barrows lies a small bowl barrow which has a mound 19m in
diameter and 1m high surrounded by a ditch 2m wide and 0.4m deep.
In 1807 William Cunnington may have found a burial in the bell barrow within
this group and in 1930 fragments of prehistoric urn were found by J S Stone on
the surface of the smaller bowl barrow.
The gas testing trenches comprise two concentric interrupted circles with mean
diameters of 182m and 364m. Where best preserved, on the western side, the
outer trench survives to a maximum depth of 1.4m and is 4.4m wide. In other
areas the trenches will survive as deliberately buried features 2.4m deep and
are marked in places by low banks up to 9.3m wide and 0.4m high. The trenches
were laid out in 1916 during experiments with gas and other forms of chemical
warfare. Their concentric design enabled gas to be released from the inner
trench and sampled on the outer one regardless of wind direction. The severe
winter of 1916 caused them to collapse but in 1918 they were re-excavated.
After a short period of use they were deliberately backfilled with the spoil
from the low banks which had lain on either side of them.
All fence posts, archaeological site markers, buildings, concrete footings and
structures are excluded from the scheduling although the ground beneath these
features is included.
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.