Colour aerial photo showing concrete runway with areas of hardstanding on either side surrounded by fields of grass and crops
About this image
Site of the former Dunkeswell Airfield photographed on 08-AUG-2007 (EHA 24672/29) © Historic England
Site of the former Dunkeswell Airfield photographed on 08-AUG-2007 (EHA 24672/29) © Historic England

The Blackdown Hills AONB and East Devon River Catchments Archaeological Survey to National Mapping Programme Standards

The Blackdown Hills Area of Outstanding Natural Beauty (AONB) on the Devon and Somerset border has been a relatively under-studied landscape. The survey was designed to provide good archaeological information to inform land management. This particularly related to potential changes due to initiatives to reduce water pollution from agriculture. These targeted the catchments of the rivers Sid, Otter and Axe. Work also focussed on major infrastructure improvements along the route of the A30/A303. This could have potentially significant impacts on the landscape along the busiest route through the AONB.

Colour aerial photograph of a rural landscape with pasture fields, woodland and some settlement
A view south over Blackdown Hills towards the confluence of the River Culm and Bolham River and the disused Second World War airfield, RAF Upottery, at Smeathorpe beyond taken on 15-Apr-14 (NMR 27979/15) © Historic England Archive

General trends

Several themes were identifiable from the survey results. It recorded ritual or religious monuments from the Neolithic to the medieval period. It also documented deserted settlements and defensive and fortified sites of medieval and later date. However,  two further themes dominated the results. These relate to medieval and post-medieval farming and industry. It seems likely that these have greatly influenced the character of the Blackdown Hills AONB.

Some of the more important findings are discussed in more detail below.

Earthwork preservation was good, with 90% of all features recorded visible as earthworks. Fewer than 7% of were visible only as cropmarks or soilmarks. This survival and the medieval character of the landscape may go some way to explain why the survey identified very little evidence of prehistoric settlement.

The inner circle revealed

Excavation in the early 20th century identified the characteristic interrupted ditches of a Neolithic causewayed enclosure at the southern tip of the Iron Age hillfort at Hembury. It is one of only four causewayed enclosures known in Devon. Lidar-derived images show a broad, shallow curvilinear ditch visible to the south. The survey interpreted this as an inner circuit of the causewayed enclosure. Recent geophysical survey supports this interpretation.

Composite illustration with left half a lidar image showing banks highlighted by shadows and right a coloured map of same
Left: An image derived from lidar data showing the earthworks at the southern tip of Hembury Hillfort, illustrating the shallow curvilinear ditch within the circuit of the causewayed enclosure. Note the linear hollows on the south-west tip of the hillfort ramparts; earthwork evidence of whetstone mining © Devon County Council.

Abbey Days – New data at Dunkeswell Abbey

The Cistercian order founded Dunkeswell Abbey in 1201 and it was dissolved in 1539. Fishponds survive to the west of the abbey and some remnants of abbey structures have been incorporated into existing buildings. However, much of the monastic precinct was demolished after dissolution.

Local writers reported in 1877 that in dry summers the foundations of the Abbey buildings were visible as parchmarks under pasture. Over 100 years later these cropmarks were recorded on oblique aerial photographs. From these the survey transcribed the plan of the east range of the Abbey. To the east of the church, are earthworks visible on lidar derived images. These may provide previously unrecorded evidence of the organisation of the monastic precinct.

A black and white aerial photo showing several buildings and an area of grass with cropmarks of rectangular structures
The hot summer causes parch marks in the grass, revealing the plan of the east range of monastic buildings at Dunkeswell Abbey on this photo taken on 25 July 1989. (DAP 6786/10 (OZ)) © Devon County Council

Forgotten Castles

At either end of a natural ridge, the earthwork mounds and terraces of Buckerell and Bushy Knap are visible on lidar derived images. These were previously interpreted as barrows, park features or simply natural knolls. Reassessment using lidar data supports their reinterpretation as small motte and bailey castles. The close spacing of the mounds and their association with a deer park to the south might support the interpretation of an evolution in function. They began with an early, post-conquest defensive role at Buckerell Knap. Over time, this progressed to a more symbolic, high status and comfortable site at Bushy Knap.

Coloured image showing a landscape outlined by shadows and highlights with two earthwork complexes situated on a central ridge
Previously dismissed as castles, the mounds at Buckerall and Bushy Knap are reinterpreted as small post-conquest date motte and baileys. LIDAR ST1201-ST1301 & ST1200-ST1300 Environment Agency DTM 01-JAN-1998 to 30-SEP-2014 © © Devon County Council: Source Environment Agency

The Blackdowns at War

The Second World War had a profound effect on the Blackdown Hills. The South-West’s landscape of rolling hills and moors, river valleys and wetlands made siting airfields difficult. The RAF saw the potential of the Blackdowns plateaux. They quickly exploited it, constructing four airfields within the project area. These were RAF Upottery and RAF Dunkeswell in Devon and RAF Culmhead and RAF Merryfield in Somerset.

The roles of these airfields evolved throughout the course of war. During the early stages of the war the airfields in the South-West largely fulfilled training, support, and coastal reconnaissance roles. As the war progressed, however, their role changed. They played an increasingly central role, both during the Battle of the Atlantic and in the preparations for, during and after, the invasion of Normandy.

Black and white vertical aerial photo showing a landscape of fields overlain with construction activity 
RAF Upottery under construction photographed by the USAAF on 09 August 1943 (US/7PH/LOC14 6028). Historic England Archive USAAF photography

Although away from the coast, the threat of invasion was also felt in the environs of the Blackdown Hills. A concentration of defensive structures and earthworks dominated the east of the project area. These are largely associated with the Taunton Stop Line, probably the most complete inland defence line in the country.

The Stop Line was constructed across the narrowest part of the South West peninsula during the early years of the Second World War. This was the time when the threat of invasion was greatest. If an invasion penetrated the ‘coastal crust’ defences, the Stop Line was intended to slow their advance.

Colour photograph of a Second World War Anti-tank gun emplacement
Anti-tank gun emplacement of Second World War date, part of the Taunton Stop Line south of Bow Bridge, Axminster. Photographs: S. Knight 2017.

The defences followed natural and artificial barriers such as rivers and railway lines. They included anti-tank ditches and concrete anti-tank obstacles, barbed wire entanglements defended by gun emplacements and pillboxes. Anti-tank mines, road and railway blocks and bridges prepared for demolition formed a further layer of defence. By April 1941 the emphasis had changed. Now the emphasis was on anti-tank islands and centres of resistance that could be defended by the limited personnel available. Because of this the in-depth defences were never completed.

Colour photograph showing a number of concrete posts in amongst dense undergrowth
Concrete posts forming an anti-tank obstacle on a railway embankment of Second World War date; part of the Taunton Stop Line south of Bow Bridge, Axminster. Photographs: S. Knight 2017.

It’s the Pits – how extraction shaped the character of the Blackdown Hills

The survey has improved our understanding of the extent of locally significant extractive industries. This includes large scale industries, such as iron ore mining and whetstone mining. It also covers smaller scale quarrying, such as gravel, sand, chalk, clay and marl extraction.

Roman iron ore extraction and post-medieval whetstone mining was very intensive. However, the smaller scale clay, chalk and marl extraction probably had the most persistent effect on the character of the AONBs landscape.

Lidar data, has allowed us to identify and record very subtle earthwork features that are sometimes not visible on traditional aerial photographs. Lidar data can also often allow us to ‘see through the trees’ to record features otherwise obscured by tree cover. This data revealed that many woods, copses and orchards obscured large disused pits. It also greatly increased the number of smaller disused pits identified in open fields. Such pits were the monument type most frequently recorded in this survey.

Many were probably marl pits. ‘Marl’ is the name given to a mix of clay and limestone used as a form of fertiliser. Marling mixed the alkaline clays with more acidic and less fertile sandy soils, reducing acidity and improving moisture retention. Pliny described marling in Britain and Gaul in the first century AD. However, it was probably most common in Britain from the medieval period, reaching a peak between the 16th and 18th centuries. It is probable that many marl pits went out of use by the 19th century when modern fertilisers made them uneconomical.

Colour distribution map showing different coloured dots against a background where different colours define different geology
A distribution map of all extractive pits and associated industrial sites recorded within the survey area. Reproduced with the permission of the British Geological Survey ©NERC. All rights Reserved.

‘Old Marl Pits’ are a common feature noted on the Ordnance Survey First Edition map. Their distribution matches the mudstone bedrock recorded by the British Geological Survey. However, it is probable this term was also mis-applied to other pits, such as clay and chalk pits.

Many old pits did not remain disused. Charles Vancouver, in his 'General View of the Agriculture of the County of Devon' in 1808, wrote:

“It is usual in the marly parts of this country to appropriate for orchards the large excavations formerly made in digging marl: here the apple trees are protected from most winds, and continue to flourish and bear longer than in less secure situations.” Vancouver 1808, 243.

Previous surveys have identified the creation of earthwork banks in orchards to improve drainage and give greater soil depth for tree planting. The surevy recorded such banks within and around many former extractive pits on the Blackdown Hills. In some cases these were even associated with former pottery industries. Many of the Blackdown Hills’ former extractive pits had a second lease of life as orchards and other woodland, which are now so characteristic of the AONB landscape.

A combined illustration of a black and white lidar image with subtle earthworks highlighted by shadows next to a historic map
An extractive pit overlain by ridges is visible on lidar images. These correspond to an orchard depicted on the OS First Edition map. © Devon County Council. © Crown Copyright and Landmark Information Group

The project

The survey examined all readily available aerial photographs and other relevant sources, such as lidar data, for the whole of the Blackdown Hills AONB excluding a small area that was assessed as part of a previous survey The survey area also included a small part of the East Devon AONB on the southern edge of the survey area and an area to the north and east. This took in the section of the A358 between Taunton and the A303 that will also be affected by road improvements. In total, an area of 546 square kilometres was surveyed.

The survey was carried out by a team from AC archaeology, hosted by Devon County Council and in partnership with Somerset County Council. More information can be found on the Devon County Council project webpages.

Colour map with extent of survey and AONB delineated against main topographic features such as roads and towns
The extent of the Blackdown Hills AONB NMP survey
The Blackdown Hills AONB and East Devon River Catchments National Mapping Programme Survey
Published 1 February 2017

A report on the aerial survey of the Blackdown Hills AONB and East Devon River Catchments.

Learn more

The images used on this page are copyright Historic England unless specified otherwise. For further details of any photographs or other images and for copies of these, or the plans and reports related to the project, please contact the Historic England Archive.

For further information on a project or any other aspect of the work of the team please contact us via email using the link below.


Colour photograph of man in dark jacket and cap

Cain Hegarty

NMP Project Manager for AC Archaeology

Cain has worked in archaeology since the late 1990s, beginning his career excavating sites throughout the Midlands. He then branched out into archaeological graphics, visualisation and the archaeological application of GIS. In the early 2000s he began working on large area aerial survey projects and has worked on similar projects to the present day. Recent work has focussed on the landscape of the South-West, from Exmoor National Park to the south coast of Devon.

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