Mapping GHQ lines in Google Earth

Well, it’s been a while since I’ve posted a blog, this one has been in the planning stage for a while now following a prolonged period of ‘writer’s block’ and a very uncooperative brain. Without further ado here it is.

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Earlier this year I was forwarded a question via a colleague. The question I was posed related to the GHQ stop-line; the defence line planned by General Edmund ‘Tiny’ Ironside in June 1940, following his appointment as Commander-in-Chief of the Home Forces on the 17th of May 1940.

The GHQ line (or General Head Quarters stop-line) was to be the final line of defence running East from Bristol to the Thames Estuary then North to Edinburgh. This line was intended to protect the industrial heartland of the country had an invading German Army managed to breach the Coastal Crust defences, inland nodal points and secondary stop-lines. This defence line consisted of Infantry and Anti-tank pill-boxes, roadblocks, barbed wire entanglements, anti-tank obstacles and trench systems.

There’s some background for you, now back to the question.

As the question related to the length of the GHQ line and the route which it followed I decided to ascertain the length of the GHQ line had it been completed and the length of the GHQ line that was actually constructed between June and August 1940. Construction of the GHQ line having been slowed and eventually halted following the appointment of General Alan Brooke as Commander-in-Chief of the Home Forces on the 21st of July 1940. Ironside was subsequently retired and the defence strategy altered significantly, but that’s another story.

Initially I thought this was quite a straightforward question and I’d find the answer in one of the many books on the subject. I was wrong; although I could find plenty of information regarding the intended route of the GHQ line (although there were some distinct differences between sources and all maps were large scale), I could not find any information about the intended length of the line had it been completed.

I did however find a reference to the length of the GHQ line in Mike Osborne’s book ‘Defending Britain’ (Buy it!) which states that the section of GHQ line running from the Bristol Channel to the River Welland was approximately 400 miles in length. However, this only takes into account a short stretch of the proposed GHQ line and doesn’t include the GHQ East line that would have run from the River Welland up to Edinburgh. The book does describe the route of the GHQ line in some detail and this information came in handy.

So, although I knew the general route of the GHQ line, I still had a job on to tie down the exact route, trace it, and determine the length of the constructed and proposed GHQ lines.

I decided to work logically, finding and pinpointing the exact route of the GHQ line, I would then plot the information into my favourite tool, Google Earth, to show the route visually and to measure its length as accurately as possible given time constraints.

I consulted my copy Henry Will’s book ‘Pillboxes’ (get one if you can!), this has not one but many maps showing the GHQ line, including a copy of Ironside’s original map of divisional dispositions which shows the GHQ line, and 1:625 000 scale Ordnance Survey maps showing various lines of pill-boxes.

Comparing the maps in Will’s book with further examples I could find in other books showed there was a general consensus about the route of the GHQ line, with some slight variations, which allowed me to narrow down the area through which it ran. There was a slight problem though as most of the maps were large scale, making it hard to pinpoint the exact route in relation to nearby towns and cities.


A quick Google search will provide you with similar maps of the GHQ line (Note the differences).

With this information the next step was to see how it compared to the archaeological record.

The Defence of Britain project was conducted between 1995 and 2002. This project aimed to record the extant 20th century military sites in the UK. The project was a huge success and the results of this project have greatly improved our understanding of the 2nd World War defensive landscape.

The results of the Defence of Britain project have been converted into a Google Earth (Available here via the ADS website) which is very useful as I love Google Earth.

With the Defence of Britain data loaded into Google Earth it is very easy check the locations of the project results, trace stop-lines, and pick out features using modern aerial photography.


Defence of Britain project overlay in Google Earth with GHQ line visible

Looking at the distribution of pill-boxes in particular, one of the main defence types that formed the GHQ lines, it was possible to quickly discern numerous stop-lines within the UK. It was then simply a matter of using the maps and diagrams I had gathered to discern the GHQ line and follow the trail of records.

Using Google Earth’s ‘Path’ tool I simply followed the route of the various GHQ lines, picking them out in a nice Red colour.

GHQ Redline.jpg

Plotting a path in Google Earth following the River Brue

While plotting the GHQ line I did encounter a number of gaps, probably due to defences being demolished, un-recorded or not constructed at all. It was clear that the GHQ line followed many of the local rivers, canal systems and many natural or man-made obstacles (Such as railway embankments & high-ground) and I was aware that this was a strategy employed in siting the GHQ lines.

Henry Wills (1985) summarises the choice of topography- ‘The GHQ line followed natural and artificial waterways, using topographical features where possible, to create a continuous anti-tank obstacle’.

To fill in these gaps in the line it was just a matter of following the river, rail or canal network the GHQ line would have followed and plotting it that way. In some areas these features were not present, which suggests that either the GHQ line had followed an anti-tank ditch, or other feature that has since been removed, I had to make an educated guess using the large scale maps I had available. We will see later this proved quite effective!

After a very short time I had most of the Southern GHQ line plotted, running parallel to the South Coast, around London and then towards Cambridge. As the line nears Peterborough the line stops abruptly. I’ve come to the conclusion that this marks the progress of the GHQ line up to the appointment of General Brooke, who gradually halted construction of the GHQ line. Quite impressive for what was at most three months work!

GHQ constructed 2.jpg

Length of GHQ line constructed

The GHQ East line, which would have run from the Thames to the Humber Estuary and through Yorkshire on to Edinburgh, is largely non-existent and as a result hard to trace. The only way to trace this route was to utilise the maps I had found, especially Will’s OS maps, and follow the major rivers and canal networks. It took a while and some detective work but eventually  it was possible to map the most likely route of this stretch of GHQ line.

ADS Yorkshire.jpg

No visible GHQ line in Yorkshire

By applying a number of methods I eventually had the GHQ line mapped in its entirety, had it been finished. It was then a matter of adding up the lengths of the various ‘paths’ in Google Earth, mainly using a calculator as I am terrible at maths. After a few minutes of calculator bashing I was left with two figures, one for the length of the line constructed and one for the length of the completed GHQ line. Success!

The length of the Constructed GHQ line was approximately 466 miles, while the completed GHQ line would have been approximately 836 miles long (This includes the GHQ Green line around Bristol, the GHQ switch-line around Swindon, the Newhaven-Hoo line and a small switch-line near Stanhope that was illustrated on Henry Will’s map).

So long story short, after a lot of work I was able to provide an approximate figure for the length of the GHQ line (both built and proposed) based on the information and tools I had available. I also had an interactive and visual means of displaying the GHQ line, which was a bonus. I sent this information off to the recipient and everyone lived happily ever after.

But that’s not the end of the story…

There have been a number of unforeseen outcomes from this little project.

My colleague, who had originally forwarded me the question, sent me a picture of a crop mark they had found while looking at the GHQ overlay. It appeared to be an anti-tank ditch. I found the crop-mark using my GHQ overlay and switching to the 1945 Google Earth aerial photography (Unfortunately not available everywhere) did indeed find an anti-tank ditch. Much of the ditch had been in-filled but it was still plain to see. The Anti-tank ditch had thankfully been recorded through the Defence of Britain project.

GHQ AT ditch cropmark.jpg

GHQ line plotted in red with linear crop-mark to the left

Now here’s the good part: The ‘path’ I had placed in this area passed directly over the anti-tank ditch! As it would have been extremely time consuming to map the GHQ line meter by meter, in some areas I had had to trace the route from afar, using my better judgement and the concentrations of records in the Defence of Britain overlay as a guide. Quite by chance I had accurately followed a single anti-tank ditch that now survived only as a crop-mark. I was well chuffed with this result!

GHQ AT ditch cropmark2.jpg

1945 Aerial Photograph showing the extant Anti-Tank ditch

Closer inspection revealed the GHQ line’s reliance on natural and man-made obstacles was abundantly clear now. This highlights the importance of looking at the wider landscape when interpreting defences from this period as opposed to looking at the defensive remains in isolation.

Okay, so ‘where next?’ I hear you ask. Well my next step is to do some further research to check the accuracy of the GHQ line that I have plotted. While writing this blog post it has become clear that a stretch of the line in Cambridgeshire that I have plotted might be inaccurate. This is due to a number of converging stop-lines in this area which makes it difficult to discern the actual GHQ line. This should only take a matter of time but does highlight the issue of conflicting data.

I have continued mapping the Second World War defences in Google Earth, including the extant and proposed Coastal Crust defences and recently I’ve started mapping Secondary Stop Lines. So, watch this space!


Henry Wills (1985) Pillboxes: a study of UK defences, 1940, [London]: Leo Cooper in association with Secker and Warburg

Mike Osborne (2004) Defending Britain: Twentieth-Century military structures in the landscape, [Stroud] Tempus Publishing Ltd

Creative Commons Licence
Mapping GHQ lines in Google Earth by Chris Kolonko is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.


2 thoughts on “Mapping GHQ lines in Google Earth

  1. I might missing something something very simple here but where can I find the Google map? I am going to be up in Bury St Edmonds in a few weeks and want to cycle some of the route.


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