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Wiltshire Walks along the Stop Line Green

By Fred Palmer

FW3/24 Pillbox on the Stop Line Green

I’ve lived in Wiltshire all my life, and have often seen individual pillboxes in fields and by streams, but never known much of their history. This changed after a chance charity shop find of an amazing book called Warwalks – Stop Line Green by a Major M. Green. This allowed me to put the pillboxes I knew into a far wider context and sparked much research into my local area. As this book showed, the individual bunkers near to me were actually part of a much larger defensive line, stretching from Highbridge in Somerset to Upper Framilode in Gloucestershire.

This article focuses on the significant part of the line which runs through Wiltshire, and details a walk which will take you along the defences.

First, some information about the entire line. The Stop Line Green (SLG), was a line of defensive structures built in England during World War 2. It was part of a wider network of defences including other Stop Lines and the General Headquarters Line. The Stop Line Green was a fall-back position, defending Bristol to allow evacuation or resupply via the docks. Wiltshire is interesting because four Stop Lines run through it, all joining to the Stop Line Green.

Original 1940s sketch map of Wiltshire showing Stop Lines Green, Red, Yellow and Blue

German tactics relied on Blitzkrieg - fast mechanised advance relying on tanks covered by air support. Therefore the Stop Lines were primarily constructed as anti-tank obstacles. The line was a continuous defence of over 100 miles, where the obstacle was provided by a river, canal, railway line, or where these did not already exist, an artificial ditch or lines of concrete cubes.

Two different types of pillboxes were used in the construction of the SLG: the FW3/24 (hexagonal) and the FW3/26 (square). Various construction techniques were used at different parts of the line, likely due to the speed of construction – it took just 4 months to build the entire defence. Many of the pillboxes have brick as their external face – concrete was poured between this and an internal formwork usually of timber. In other places, timber formwork was used both inside and out of the pillbox, resulting in an external concrete finish.

For most of the Stop Line Green in Wiltshire, the River Avon is used as the obstacle. This continues from Avoncliff to Malmesbury, approximately 25 miles, after which the line continued as an artificial anti-tank ditch.

Almost all of the SLG is visible from public footpaths, so this article will locate both the defences and a possible walk route to follow. As the Stop Line Green is a linear defensive obstacle, it is best experienced and understood as a linear walk. However, some parts are more complete than others, and can be explored on their own.

I’ve split the line into sections, which all have their own character and use the landscape in different ways to provide defence. Each section starts with an excerpt from a British Reconnaissance report dated 18th June 1940, detailing how that part of the line works.

For further information, the best resource is the Extended Defence of Britain Google Earth overlay. This has details of thousands of British defensive structures, and lots of detail. The Pillbox Study Group also have a large repository of information of the whole of Britain.

Original reconnaissance report for the Stop Line Green dated 18th June 1940

1. Freshford - Bradford Junction

FW3/24 grid reference ST 8000 5989

“From MIDFORD HILL the F.D.L. passes across the LIMPLEY STOKE tongue and drops to the AVON VALLEY and FRESHFORD 2280. An artificial obstacle is required in this sector.

The line of the River AVON is followed. This is a complete anti-tank obstacle....”

The Stop Line Green drops down into Freshford, where it joins the River Avon. In this first section, the Kennet and Avon Canal and the Great Western Railway also provide effective anti-tank obstacles. Bridges and aqueducts which cross the obstacle are heavily defended by pillboxes, often in pairs: One pillbox being forward of the defensive line and one being sited close to the bridge. The main bridges were mined with explosives, meaning the defence focused on being able to demolish these before the attackers arrived.

In Bradford on Avon, some ‘dragons teeth’ concrete cones can be seen next to the railway line. In wartime, these would have likely been across the rail bridge itself to create a tank trap.

Most of the pillboxes in this section are very prominent and close to the footpaths. An FW3/24 Pillbox in Bradford-on-Avon has a plaque explaining its role in the defence. Another particularly noticeable FW3/26 Pillbox is across from the Cross Guns pub, defending the Avoncliff Aqueduct. This part is very accessible, parking is easy in Bradford-on-Avon and there are plenty of nearby pubs.

The SLG between Freshford and Bradford-on-Avon

2. Bradford Junction – Whaddon

FW3/24 grid reference ST 8760 6177

“The line of the River AVON is followed. This is a complete anti-tank obstacle....

Near STAVERTON 2980 the KENNET AND AVON canal approaches from the East ....The canal ... form[s] the F.D.L. of defensive positions running Eastwards towards READING...”

To the east of Bradford-on-Avon the landscape widens and flattens. Here, the River Avon is still the principle anti-tank obstacle however an additional line of defence is provided by the Great Western Railway (still existing) and the Wilts, Somerset and Weymouth Railway (now disused). Pillboxes are sited back from the river, and often in front of the railway embankment, which avoids them being silhouetted against the sky. Staverton Railway Junction was particularly heavily defended, and the railway bridge over the Avon would’ve been mined with explosives.

Whaddon is a particularly interesting village as it is where the Stop Line Blue meets the Stop Line Green (see below map). It was designated as an ‘Anti-tank island’, a particularly strong defensive element which can be seen with the numerous existing defences. The meeting point of the two lines is interesting for its contrasting pillbox types - whilst the Stop Line Green only has types FW3/24 and FW3/26, the Stop Line Blue only has types FW3/22 and FW3/28. This shows how separated the design and construction of each Stop Line was. For more information on Whaddon, see the Hidden Wiltshire article here.

The most accessible parts are to the immediate east of Bradford-on-Avon, and around Whaddon, which has a high density of different defensive structures.

The SLG between Bradford-on-Avon and Whaddon – Note Stop Line Blue around Whaddon

3. Whaddon - Christian Malford

FW3/24 grid reference ST 9436 7489

“The line of the River AVON is followed. This is a complete anti-tank obstacle as far upstream as CHIPPENHAM 3694, after which it cannot be relied upon and local improvement may be necessary.

...There is an unsatisfactory sector near LAYCOCKS 3689 where the position is badly overlooked from the high ground at BOWDEN PARK 3888.”

This is the longest sector of the same defensive ‘type’ along the entire Stop Line. Pillboxes are sited on slightly higher ground, generally to the west of the River Avon.

At Lackham College, a potentially weak salient was created as the River Avon curves sharply eastwards. In other parts of the line this was avoided, however this was mitigated here with a high density of pillboxes, and the reliance on the Avon as a ‘complete’ obstacle.

Some defences still survive to the immediate north of Whaddon. However, further north towards Melksham is fairly inaccessible, with footpaths being very overgrown and disused. Also to the north of Melksham there is very little evidence of the Stop Line, and the footpaths are again difficult. The SLG becomes accessible and visible again around Lacock, where you can walk to Chippenham along footpaths with good views of pillboxes. To the immediate north of Chippenham there is also a section of the line in good condition, but only as far as Tytherton Lucas, beyond which there is no trace of the SLG until Christian Malford.

The SLG from Lacock to Chippenham

4. Great Somerford

FW3/24 grid reference ST 9720 8252

“In the sector from MALMESBURY to GREAT SOMERFORD the River AVON is often wide, swift and shallow with indifferent banks and hard bottom and cannot be relied upon as an anti-tank obstacle.”

At Great Somerford, the Stop Line leaves the River Avon and instead follows the Malmesbury Branch Line Railway. The railway had been closed since 1933, allowing pillboxes to be built on the embankment, overlooking the flat surrounding countryside.

This is also the point where the Stop Line Red joins the Stop Line Green. Several pillboxes of the Stop Line Red are still existing to the north of Braydon Brook, but are not visible from public footpaths. How exactly the two lines met is not clear, both from the ground and using historical aerial photography.

The southernmost pillbox of this section is only distantly visible on an underused footpath, however the other three can be easily seen from the road.

The SLG around Great Somerford – Note Stop Line Red to the northeast

5. Malmesbury – Fosse Way

FW3/26 grid reference ST 9175 9147

“From the bend in the river at 363106 the F.D.L. leaves the River AVON and runs North and North West over the COTSWOLD PLATEAU making use of the best tactical ground....

This is a weak sector from the point of view of anti-tank defence and an artificial ditch should be constructed if the excavators are capable of working the soil, which is limestone, in places thinly covered with earth.”

Revision (not completed):

“(c) The task of constructing an artificial obstacle across the COTSWOLD Plateau in the sector MALMESBURY - AVENING 3218 is a difficult one owing to the hardness of the ground. In order to take advantage of a partial anti-tank obstacle as far as possible the lines will now run along R.AVON to ESCTOURT Ho.3411- TETBURY - thence ry to about 349147 – AVENING.”

To the south and east of Malmesbury the River Avon is still the principle anti-tank obstacle, however it is reinforced at Cowbridge with anti-tank blocks. These are overlooked by two pillboxes, and the bridge was mined for demolition.

At Malmesbury, the defensive line leaves the River Avon, and an artificial anti-tank ditch becomes the main obstacle. No trace of this obstacle is visible on the ground, however many traces of it are visible on modern satellite photography.

FW3/24 pillboxes along this sector are situated relatively close together, often within sight of each other. The land is gently sloping, and generally the pillboxes are placed at high points to give them the greatest view. They are also sited at places where the ditch changed direction.

Many of the pillboxes are not on publicly accessible land, however there is a well preserved and accessible section around the Fosse Way, which also provides the county boundary with Gloucestershire and therefore the end of our tour.

The SLG around Malmesbury – Note the anti-tank ditch providing the continuous obstacle


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Rich Leahy
Rich Leahy
Mar 20

Recently walking along the Ridgeway on Hackpen Hill in Wiltshire and I saw a round brick construction in a farmers field. I had a look but there’s nothing to say what it could be. There’s an open manhole but all it shows is an underground area. I’m presuming this was a gun emplacement. I dropped a pin. See picture


Jeremy Riggs
Jeremy Riggs
Apr 19, 2020

Thank you for this marvellous article. I see these pillboxes all the time and apart from assuming they were defensive structures built during WWII I had little knowledge of them. After seeing some new ones recently it occurred to me that it would make a good read for the hiddenwiltshire site.

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