Bell barrow, three bowl barrows and gas testing trenches on Idmiston Down


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:


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The building or site itself may lie within the boundary of more than one authority.

Wiltshire (Unitary Authority)
National Grid Reference:
SU 22212 36615

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 protection. 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.

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.


The contents of this record have been generated from a legacy data system.

Legacy System number:
Legacy System:


Books and journals
A Brief History of the Chemical Defence Establishment, Porton, (1961)
Carter, G B, Porton Down 75 Years of Chemical and Biological Research, (1992)
Colt Hoare, R, The Ancient History of Wiltshire: Volume I, (1812), 217
Colt Hoare, R, The Ancient History of Wiltshire: Volume I, (1812), 217
Foulkes, C H, Gas! The Story of the Special Brigade, (1934)
CBA Research Report 12, Wilson, D R (ed), Aerial Reconnaisance for Archaeology, (1975)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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