This blog post was triggered by a post on the Lidar & Aerial Archaeology facebook group by John Rowley on 24th February 2026.

The post was regarding a feature of two neat concentric circles recorded from a crop-mark on Hepscott Manor farm, near Morpeth, Northumberland, from a 1958 aerial photograph by Historic England Aerial Mapping Explorer.

Historic Environment Record No: N11704
Historic England Monument No: NONE GIVEN
Date: NEOLITHIC\BRONZE AGE
Interpretation: HENGE\CIRCULAR ENCLOSURE
Seen as: CROPMARK
Source: HISTORIC ENGLAND ARCHIVE RAF/543/318 F22 360 08-JUL-1958

Keys to the Past: N11704
"A circular cropmark on an aerial photograph can be seen, but its date and function is unknown. However, the circular cropmark could also be a modern feature; only further investigation will throw some light on this site."

This record informs us that it was recorded by Historic England as part of the AERIAL INVESTIGATION AND MAPPING, South East Northumberland Extension Project.

Deegan, A. (2022). South East Northumberland Air Photo and Lidar Mapping Project. Leeds: Alison Deegan Air Photo Interpretation and Mapping.

The location of the circular enclosure is: NZ 2144 8315

Clearly HE had some doubt about its age and original purpose and seemed to me a sensible cautious interpretation.

The feature is not visible as an earthwork on LIDAR. However, examination of historic satellite imagery on Google Earth showed that the cropmarks were faintly visible in several years: December 2002, May 2018 and May 2020. The circles lie just east of an old field boundary (shown on early OS maps).

It just seems too neat to be anything prehistoric but if modern, what could it have been?

Some research led me to post the following comment:

"Agree its quite hard to see on Google Earth but it does look overly neat for something prehistoric. There was a small airfield at Hepscott Manor used in 1933. Wonder if that could be associated?

HEPSCOTT MANOR: Temporary aerodrome
Operated by: Sir Alan Cobham's National Aviation Day No.2 Tour' Period of operation: 28th July 1933
https://www.ukairfieldguide.net/airfields/Hepscott-Manor

Thinking that it could have been a temporary marker of some kind for the 1933 air-show I thought, if that, it would have been carerfully measured for the event. Although not easy to measure precisely on the GE satellite images, some experiments suggest they may originally have been circles of 400 feet and 200 feet in diameter. If so, that could well support the idea that they were originally an aerial marker.

There is also nothing to suggest some kind of WW2 activity in the area such as a searchlight, anti-aircraft or radar installation on the Defence of Britain interactive map. 

Looking at old maps shows that the N-S field boundary along the SW edge of the outer circle was removed relatively recently. The older boundary which joined that and crossed the enclosure from SW-NE is shown on the 1st edition OS (c.1860) but appears to have been removed by the 2nd edition (c1900).

The images and notes shown below were copied from the UK Airfield Guide for Hescott Manor (originally provided by Michael T Holder).

An online exhibition at the RAF Museum provides much information about the life of Alan Cobham. See also this short clip on Pathe News which also has an clip of the Irish Aviation Day. There is also much more information about Cobham's Air Circus on A Fleeting Peace.

The National Aviation Day campaign, known as ‘Cobham’s Flying Circus’, toured Great Britain, Ireland and South Africa, between 1932 and 1937, giving many their first experience of flight.

Cobham’s Flying Circus toured between 1932 and 1935 taking 990,000 people on flights in his fleet of aeroplanes with over 3,000,000 people visiting the display.

Several events at the air-show may have needed a large marker visible from the air: flour bombing competition, helicopter landing, marker for the air race or parachute landing.

I am aware that this is a very speculative post. The measurement of the circles, although prone to some error, seems, along with their neat appearance, to support a modern origin. Whether it can really be linked to Cobham's Flying Circus I can't of course be sure. The relationship of the concentric circles to the now removed field boundaries is also uncertain in my opinion.

A prehistoric henge from the Neolithic. or double ditched enclosure from Bronze or Iron Ages, is always a nice find, but so in my mind is a physical link to the exciting world of the 1930 aerial extravaganza that was Cobham's Flying Circus.

Unless there is more investigation here, and even then, we'll probably never know which is true.

 Alison Deegan. When You Have Eliminated the Impossible...
AARGnews, 72, April 2026, p.38-40.

Alison uses the above example in an article about the difficulty and hazards of interpretation of lidar and aerial imagery with regard to her discovery of an unusual site above the Lune valley on the western edge of the Howgill Fells of  Westmorland:

She describes:
A tiny cluster of at least 15 small circular platforms were discovered on lidar imagery of the open moorland in the north of England. Without the benefit of ground investigation, the working hypothesis is that they are platforms or stances
for timber houses, possibly Bronze Age. However, unenclosed platform settlements are very scarce in the north of England, so could there be an alternative explanation?

Below are my lidar images made from DSM using Prismatic Openness and VAT blends provided by the RVT Plug-in for QGIS.The third image is VAT overlaid with contours at 5m.

And, no, I have no idea what the circular features scooped into the hillside might be. I always find I look for alternative explanations (in this case geology and glaciation) but in that way you can also miss the archaeology.

I also uploaded a 3D Lidar Landscape model here:
https://skfb.ly/pJvNr

Iron Age hillfort & Roman Signal Station on Barcombe Hill above Vindolanda Roman Fort, Northumberland.

Location: NY 7830 6681

Keys to the Past: N6569

Scheduled Monument: 1018536

3D LiDAR landscape on Sketchfab: https://skfb.ly/pGKN9

Location: NZ122248

The complex prehistoric and industrial archaeology of Cockfield Fell as shown on an enhanced lidar image.

Three non-defensive enclosures (two rectilinear and one oval) may be late prehistoric along with the remains of field systems and possible unenclosed round houses. A poorly preserved square-walled enclosure with attached remains of a small rectangular building is probably medieval.

Coal mining began here in the 14th century revealed by the dark depressions of a large number of small bell-pits, Larger and deeper pits with associated spoil heaps continued later. Deeper mining is responsible for the marks of mining subsidence over much of the area. In the 18th century shafts gave way to drift mines and tramways were built to transport coal from the pits to a local railway following the valley of the River Gaunless, completed in 1830. A branch line was built across the fell in 1863 crossing the River Gaunless and former railway by an impressive viaduct.

Sandstone quarries were opened close to the village. More dramitic were quarries crossing the fell following a whinstone dyke, used for road stone. Part of the east quarry has been infilled but revealed by its huge fan-shaped spoil heaps on its N side.

Scheduled Monument: 1002314

3D Lidar landscape on Sketchfab: https://skfb.ly/pGDPI

Roberts, B. K. (1975). Cockfield Fell. Antiquity 49. Vol 49, pp. 48-50.

Strangely what brought me back to Cockfield Fell (virtually this time), long after my visit in 2015 was the chance discovery on social media of Dixon's Experimental Canal supposedly dug here in the 18th Century. Was that actually true - there seemed to be nothing in the archaeology record? If so, where was it on the lidar image?

THe above appears on page 76 of the reserach document:
THE 1830 S&DR HAG GERLEASES BRANCH LINE HISTORIC ENVIRONMENT AUDIT
The Friends of the Stockton & Darlington Railway and Archaeo-Environment Ltd. March 2022

The rectangular cut feature so described is located at NZ 1177 2546 and clearly shown on the lidar image.between the long cut of the Haggerleases stone quarry and the ruin  of Millfield Grange. The drain running north from the north side of the pond is also shown. Other areas of disturbance close-by are recorded on the HER and Historic England as quarries, or drifts to mine stone underground.

Measured from the map, the rectangular cut (labelled as a pond on large scale later OS maps) is approximately 27m (90 feet) long and 5m (16 feet) wide.

The entry for the feature on the Historic England Aerial Mapping Explorer is given below:

Monument Number 1052156

Hob Uid: 1052156 
Location :
County Durham
Cockfield

Grid Ref : NZ1177025470

Summary : A small rectangular pond of post-medieval date is visible as earthworks. The feature remains extant on the latest 2015 vertical photography.

More information : On Cockfield Fell at NZ 1177 2547, outside the area of RCHME large-scale survey (1a) and not noted by Roberts (1b), is a large rectangular pond of post-medieval date on the lip of a steep north-facing slope. It still holds water. (1)

The small post medieval rectangular pond is visible as an earthwork on air photographs and lidar, centred at NZ 1177 2547. The pond is first depicted on the 1897 edition Ordnance Survey map and is probably associated with mining on Cockfield Fell. The feature is defined by a rectangular depression with an embankment on the downward slope. It remains extant on the latest 2015 vertical photography. This feature was mapped and recorded as part of the Stockton and Darlington Railway Heritage Action Zone Aerial Investigation and Mapping project.
(2)

"In the late 1760s, moving coal was often the hard part. A canal offered a huge advantage: heavy loads could be shifted with a fraction of the effort compared to carts and rough tracks across the fell. Dixon cut a short trial section and even set a flat-bottomed boat on it to prove the concept."
George Dixon's Canal by Northern Perspectives UK on YouTube. 

Canals, coal and the birth of Dixie.
The Northern Echo,15th June 2002.

"Back on the fell, brother George was doing all kinds of experiments. He was producing gas from coal, and his house in Cockfield became the first in the country to be so illuminated.

But George was frustrated. He had inherited the mines, but apart from keeping him in interesting experiments they were not much use, unless he could find someone to buy the coal.
Cockfield Fell, up the Gaunless Valley, is miles from anywhere, so George resolved to build a canal from the fell to the River Tees around Winston. Then he would dig the Tees out and sail his boats to Stockton, and from there on to the huge London market.

To prove he could do it, he dug a stretch of canal on the fell and built a flat-bottomed boat to sail on it. When it worked, he was so excited that he called his friend, landowner Lord Barnard, of Raby Castle, to come and have a look at it.
But Lord Barnard was not impressed. He was not going to contribute financially to any such barmy project, and he certainly was not going to have waterways wandering across his land.

Undeterred, George called a meeting of entrepreneurs in the Post House, in Post House Wynd, Darlington. The meeting included the grandfathers of Edward Pease and Jonathan Backhouse, who later played key roles in creating the S&DR.

That 1767 meeting instructed a surveyor to draw a canal between Winston and Stockton, passing through Cockerton.
Although the canal was never dug because of the expense, it was the first time anyone had thought of linking the coalfield of south Durham to the sea.

The idea resurfaced in the early 19th Century. The plans were resurrected and modified, and ended up as the Stockton and Darlington Railway, linking the coalfield with the sea."

And in the same reference:

"COCKFIELD Fell is probably England’s largest ancient monument. It is a wonderful and windblown place, with all of the North- East’s history laid out amid its lumps and bumps.

From pre-Roman farmsteads to very early factory farming of rabbits, from the first inland deep mine in the country to 400 or more bell pits, from the canal that inspired the Stockton and Darlington Railway to a steaming express line built by one of the greatest Victorian engineers – all is there on Cockfield Fell."

Bleak and charmless – the fell is a hard place to fall for. The Northern Echo, 5th February 2009.

There’s no flower blooming fair,
Upon Cockfield Fell
That with fragrance fills the air,
Upon Cockfield Fell.
And far distant be the day,
When again I’ll wearied stray,
O’er that unfrequented way,
Upon Cockfield Fell

There are no leafy trees
Upon Cockfield Fell,
To protect me from the breeze,
Upon Cockfield Fell.
There no pleasant streamlets flow,
There the vagrant bees ne’er go
For no pretty flowers blow,
Upon Cockfield Fell.

The 'Roman Graves' on Cockfield Fell

Keys to the Past: D57309

One of the main archaeological features removed by the DTM algorithm (retained on DSM as can be seen by comparing the images below) are five small rectangular banked enclosures, apparently open on their northern side.
Historic England (Monument Number: 882410) claims there are six of these but their eastern one (from aerial photographs) doesn't show up well on the lidar.

They are located on both sides of an old trackway close to a prominent coal shaft at NZ 1219 2495. There are no other similar structures visible on the surrounding fell.

The banks are said to be known locally as 'Roman Graves' and some have been dug into with apparently no finds made. The external banks are recorded as being 0.6m high. The enclosures are all roughly the same size, varying from 7.0m-9.0m internally by approximately 6.0m-8.0m transversely, the longer axis being generally E-W. All are distinguished by containing within them from one to five parallel earthen banks up to 0.4 m high (?stalls for horses).

It seems to have been suggested that they may have been pillow mounds (artificial rabbit warrens) but there seems to be no evidence for that and they are probably more likely associated with coal mining or other industrial activity.

The large almost square enclosure is described here (HE: 22089) and not considered as Roman or Romano-British.

LIDAR (DSM & DTM, 1m) copyright Environment Agency (2022).

Enhancement of the LIDAR was carried out using tools made available in the QGIS plugin, Relief Visualization Toolbox. Kokalj, Žiga & Hesse, Ralf. (2017). Airborne laser scanning raster data visualization: A Guide to Good Practice.

Location: NZ 2788 7685

Low mound almost 100m diameter and approximately 1.5m high, sitting in what was the corner of a former field. Could be modern (coal workings?) or older. Nothing revealed by examination of old maps, historic satellite images, aerial photographs or on recently published Historic England Aerial Mapping Explorer.

The Coal Authority map indicates probable shallow coal mine workings in a boad area including the mound, but no pit shaft at its location.

The only thing identified on the Northumberland HER in the vicinity is an 'area of ridge and furrow east of the A189 near Cramlington' (N28438). This is shown as including the two fields located south of the boundary (S of the mound) and N of East Cramlington Farm.

Two blocks of medieval or post medieval ridge and furrow are visible as earthworks and cropmarks on historical air photos. The lidar imagery indicates that the earthworks survive. These features are arranged in two large blocks with east to west aligned furrows.

It is not readily apparent on current lidar.

Just for fun - some modern landscaping in recreational areas surrounding Newcastle Great Park. 

Blakehope, Otterburn, Northumberland.

The monument includes the remains of a Roman fort contained within the partial remains of a larger Roman temporary camp, situated on gently sloping ground adjacent to the Dere Street Roman road. The Roman fort is visible as a rectangular enclosure with rounded corners measuring approximately 128m by 119m and orientated NW to SE; it is defined by a single turf built rampart with an outer ditch visible as intermittent low earthworks. There are at least two recorded entrances. A small excavation within the Roman fort indicated it to be pre-Hadrianic in date. The fort is situated within a larger enclosure, interpreted as a Roman temporary camp. This enclosure is defined by a rampart with an internal and external ditch which are partially visible as slight earthworks on the W, N and NW sides. The temporary camp is cut by the Roman Road Dere Street indicating that the road is later than the camp.

Scheduled Monument:
https://historicengland.org.uk/.../the.../list-entry/1006507

Keys to the Past: N8278

Location: NZ 2292 7501

Probable Romano-British enclosed settlement.

There are few survivals of such earthworks in this area of North Tyneside although there are many crop- and soil-marks of similar enclosures recorded from aerial photographs. These have been mapped recently by Historic England on their Aerial Archaeology Mapping Explorer.

"First reported by Tim Gates on 20th January 1983, and later in more detail on 26th October 1984. An enclosure defined by a trapezoidal ditch - certainly the remains of a settlement of R/B type. The surrounding area is covered by later agricultural earthworks and the interior has similarly been ploughed. The ditch is quite pronounced though, being up to a metre deep at the rear (west) of the enclosure, but shallower on the east side where the entrance may have been. Possible moated site."

Tyne & Wear SiteLines: 1323

There are extensive remains of [Medieaval, broad] ridge and furrow in what later became Gosforth Park. It survives in the fields and woods north of the old tramway, patchily between the tramway and the racecourse, and very well under the golf course within the race track. Much is clearly visible, but there are places where it is apparent only on aerial photos. Most of it runs roughly north-south; there are some distinct blocks (furlongs); curved and straight ridges; a range of widths from 5.5 to 11.5 metres; and a patch of double-crested ridges. There are also probable traces of enclosure banks which were later removed for the park.

A rare survival of the former common fields of Gosforth Common.

Tyne & Wear Sitelines: 165

Gosforth Park, Brandling House (Gosforth Hall or House)
Tyne & Wear Sitelines: 7701