Marchwood Inclosure’s Concrete Base or Plinth

In 2020 I heard about a mysterious hexagonal concrete block located in the middle of the woods in Marchwood Inclosure, New Forest. As a documenter of wartime history locally, I went to examine it to try to understand a little better what purpose it served.

Locally there have been various theories as to what this 6-sided concrete block is. These include it being the base for a Second World War spigot mortar or searchlight, a mount for a barrage balloon, or surprisingly (given its size) a pillbox.

Whilst I understand why many of these theories have been mooted, once I visited the site, the design and location of the concrete plinth didn’t really provide evidence for any of those theories to be true.

My first impression was that it was from the World War 2 period. I based that theory on the fact the Royal Observer Corps (ROC) had a position close by overlooking the Ipley Crosswords during the Second World war.

However, I now don’t believe the concrete block was built during the Second World War at all, but instead predates that period and is from the First World War era. 

Below I will explain the process that took me to the conclusion on what I believe the Marchwood Inclosure concrete plinth to be, and why I’ve discounted all the other theories. 

Debunking the theories

Why it isn’t a pillbox

Let’s just start with the easiest theory to disprove; that it’s a pillbox. People who say this obviously haven’t visited the site and have just seen photos. Reason being, when you see the concrete plinth in isolation, then yes, to the casual observer it might appear to look like a WW2 pillbox.

However, when you put a grown man and a 7-year-old boy next to it, the scale soon becomes clear. 

It’s not a Second World War pillbox… unless it’s being used by the pixies from New Forest folklore. 

Why it isn’t a barrage balloon base or mount

Admittedly it is of a similar size to the concrete bases barrage balloons were flown from during the Second World war. But, unlike barrage balloon mounts, it doesn’t have a loop and ring to attach the balloon cables too.

Instead, it has a threaded bolt on it. 

Also, it makes no sense that you would have just one barrage balloon on this location. Barrage balloon mounts come in a set, as they were flown in groups to protect a location.

One lone barrage balloon would not have been flown here, and more’s the point, what would it have protected? There’s nothing here historically during WW2 (aside from a 3-man ROC post nearby) that would have necessitated barrage balloon defences. 

Why it’s not a spigot mortar base

I can see why some people would think that the concrete in Marchwood Inclosure is a spigot mortar base. It does have a similar shape to it and has the threaded bolt, which could appear to be a similar shape to a spigot rod.

But there are some key differences between the concrete in Marchwood and a WW2 spigot mortar base. Those differences are:

• Most spigot mortar bases (but not all, including the one shown above) tended to be cylindrical, not hexagonal. 
• Spigot mortar bases tended to be dug into the ground, offering cover to the men manning the position. There is no evidence of a dug in position around the Marchwood concrete. 
• The threaded bolt in the Marchwood concrete is not stainless steel and shiny like a spigot rod, or as thick.
• The position of the Marchwood concrete offers no visibility of the road which would be the obvious route for any enemy coming from Beaulieu if landing on the river, heading towards Marchwood and Hythe. 
• During the Second World War, Marchwood Inclosure had no trees like it does today. The trees there were planted post-war. You would not have a spigot mortar in such an open and visible position with no camouflage or cover. 
• Spigot mortar bases have a convex and domed top. The Marchwood concrete doesn’t. 

Why it’s not a searchlight base

Like the spigot mortar theory, we must again consider how Marchwood Inclosure was open land during the Second World War, and not dense with trees.

It would mean having a searchlight position completely out in the open, and permanently set into the land.

Some searchlight positions in the New Forest like this tended to be mobile units, taken to different locations when towed by trucks. 

Fixed searchlight positions that existed in the New Forest don’t have concrete plinths remaining in them. But they do have a large cut out and depression in the earth for the searchlight to sit in, which this doesn’t have.

Why it’s not a trigonometry point

A triangulation station, also known as a trigonometrical point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity.

The concrete in Marchwood Inclosure looks nothing like one. For comparison, here’s a photo a real trig point station I took at Yew Tree Heath in the New Forest.

Why it isn’t anything to do with the Royal Observer Corps

I spent a lot of time on this one, and for good reason too. The concrete plinth in Marchwood is just a few minutes’ walk from the position of an ROC post that was in the Inclosure during the Second World War. 

If you walk to the end of Marchwood Inclosure and stand on the hill overlooking Ipley Crossroads, you will see brickwork poking out of the ground. During the 1940s this was a small brick structure used by volunteers of the Royal Observer Corps to look out for enemy planes.

Is this just a coincidence?

You might conclude that the concrete in the woods had something to do with the ROC. Perhaps it was a plinth for them placing their equipment on? 

However, I was able to debunk this one in several different ways. 

The first thing I did was contact the ROC Museum to see if the concrete looked like anything they would have used historically. After some back and forth on email, it was a resounding no.

Here’s a quote from our email exchange.

The concrete block is not ROC related, whatever it is. The ROC in their aircraft observation role operated from some form of structure, initially they were self-build of any material to hand and later as they became worn out were replaced by brick or concrete structures with an open top where two observers would stand, one using instrument, the other spotting and reporting any aircraft movements. Each Post had a wooden hut on site often incorporated into the Post structure. There would be no possible need for a huge block of concrete.

The next consideration that helps to debunk the concrete block being used during the war by the ROC, is when you examine aerial photography.

This was pointed out by local historian, Anthony Pasmore. He noticed that there was no clearly trodden path from the site of the ROC position to the concrete plinth. You can see that in the Luftwaffe aerial photo below which dates from the Second World War. I’ve highlighted both positions.

Given that Marchwood Inclosure was open land at the time and didn’t have the dense trees it does now, there should be a direct path if it was related to the ROC position. After all, why waste time in a national emergency by going in a loop between both points? 

So, what is the concrete block in Marchwood Inclosure then?

I believe that it’s something connected to early 20^th century anti-aircraft systems, known as a “ranging station”. 

An anti-aircraft site from 1917 known as a ranging station

I came to this conclusion after a chance conversation with Anthony Pasmore. He encouraged me to visit the New Forest Heritage Centre’s library in Lyndhurst and read the Verderers’ meeting notes from the last 100 years. 

Within the meeting notes is series of letters and meeting notes. One of these is dated the 21st of September 1917. It’s a letter requesting permission to place concrete for anti-aircraft height finding purposes to the west of Applemore.

Here’s that 1917 letter (apologies for the poor quality scan). 

It’s not that easy to read, so I’ve transcribed it:

First line of address and name illegible
Headquarters
High Street
Portsmouth

21 September 1917

Dear Sir, 

Southampton Anti-Aircraft Sites

I am instructed to inform you that is it proposed to place a small concrete bed (might say “base”, not legible) for height finding purposes on the Heath Land immediately to the West of Applemore Hill in the parish of Denny Lodge.

I cannot at the moment give you the exact site, but the actual land which will be occupied will be extremely small and I conclude there will be no objection to the occupation.

Yours Faithfully,

LW Carr Lieutenant Asst.
War Dept. Land Agent 
Montague Chandler Esq.
Abbey Water
Romsey

There are then further notes from 1917 where the Verderers make no objection to the concrete being placed to the west of Applemore Hill and Denny Lodge – which I assume relates to the area we know today as Marchwood Inclosure.

Pasmore has previously commented on this too, in one of his local newspaper columns:

One final and very small military land-take of 1917 was of an entirely new type and has actually proved one of the most durable relics of Great War activity in the Forest. A site was sought for the construction of a concrete base to support height-finding equipment to assist the anti-aircraft defences of Southampton. It was to be located west of Applemore Hill and this substantial structure may still be seen, although now concealed in the conifer plantation of Marchwood Inclosure.

You might think it sounds strange that anti-aircraft precautions were being taken in the New Forest in 1917. However, London was bombed from the air in 1917, so early warning systems were already being set-up around Greater London.

A German Zeppelin had also flown over Portsmouth Dockyard on the 16^th of September 1916, dropping 4 bombs. No damage occurred, but this could have been a consideration on why steps needed to be taken to protect Southampton.

Southampton docks had to be considered a risk. That could account for aircraft height finding equipment being placed locally to support anti-aircraft defences.

If you look closely at the concrete block in Marchwood Inclosure, there’s also a cut-out on one side, and evidence of wiring. This could be for early telephony or electrics – both technologies were used in anti-aircraft systems in this period. 

The construction of the concrete plinth

Here are some photos I took and notes.

Firstly notice how on the top of the concrete is a triangular indent on the top with 98cm length sides. I believe a compass direction dial would have been here… sadly I have no historical imagery.

There is also a threaded bolt in the centre in the middle top. 

In the side of the concrete block there is a square cut out with evidence of electrics at top and possible socket at bottom. The electric wiring could point towards an early 20th century telephone operation.

There is also a hole off centre on the top (I am not sure if hole is deliberate or damage). It could be where any possible electrics came up through.

I’ve managed to track down more examples of ranging stations that appear to be identical to the one found in Marchwood Inclosure.

It’s interesting that they are often mis-identified as being of Second World War era.

West Common, Gerrards Cross, Buckinghamshire

This has been described as a barrage balloon mount in Mike Osborne’s book, “Defending Britain”. It’s not though.

The Defence of Britain Archive also doesn’t believe this to be the case, and also discounts it being a spigot mortar mounting (see record).

Near Abinger Common, Surrey

This one below I found on the Geograph website. As with the one in Buckinghamshire, the Defence of Britain archive are still not sure what it is (see record).

Here’s another photo of it where you can see the triangular indent similar to Marchwood’s concrete. These images were found on the forum of the Pillbox Study Group – you can read their discussion here.

There is also a threaded bolt, but it has been bent over (hard to see in the photo).

Buckland, Oxfordshire

This one comes courtesy of Max Rice, someone else who has researched these too. As you can see, this one hasn’t weathered too well over 100 years!

Earlswood, Redhill, Surrey

And here’s another in Surrey. This has previously been correctly recorded as a ranging station.

West Brunton, Newcastle

There’s also one that was correctly identified as a ranging station in Newcastle-upon-Tyne (sorry no photo)

The team who discovered this one said:

“One of three such sites (used to be one at Kenton plus a third unknown site). Used to triangulate the altitude and range of a zeppelin. It consists of a circular reinforced concrete base with a telephone point, but the compass direction dial has gone {1}. The circular planar surface is 1.5m in diameter and 0.6m high. Contains a recess for a field telephone connected to the anti-aircraft guns command post.”

To conclude, the concrete in Marchwood would have had height-finding equipment placed on top, they could measure the distance to enemy aircraft (or Zeppelins), and then phone that information back to the anti-aircraft position.

However, I don’t believe the Marchwood ranging station was ever used in anger.

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