Miles Kington: Strange relics of Wiltshire's forgotten Maginot Line

'The tank traps, pillboxes and bollards lay silent, waiting for the blackberries to grow on them'

My father-in-law was in the Tank Regiment during the war – he was most distressed to hear of the death of his old commander, Michael Carver, the other day – and I suppose that it is because of his continuing interest in tank warfare that I, who have very little interest in war of any kind, keep my eyes open for scraps of tank information that might come my way.

I have recently been working on a forthcoming Radio 4 series about General de Gaulle, and I had never realised just how convinced the old general was of the importance of tanks in the coming war. All through the 1930s he preached the gospel of tank superiority, and it was France's bad luck that nobody paid him any attention, except perhaps the Germans. It was thanks in large part to their tank strength that they were able to sweep across Belgium, Holland and France, encountering only the occasional setback (one of them because of opposition from de Gaulle's tanks).

All this is a long way from where I live on the Wiltshire-Somerset border. There are signs of warfare round here, of course. There are Arthurian battle grounds (doubtful) and castles knocked down in Civil War sieges (nearby Farleigh Hungerford castle, never rebuilt) and even, on our local church door, damage which is said to have been done by Vikings trying to get at the terrified folk seeking sanctuary inside. But the only local legend about the Second World War concerns an underground motor bicycle factory at the village of Westwood – apparently a large part of the production of wartime Enfield motor bikes was housed beneath what is now a big green field, to avoid aerial observation.

However, none of this explains the fact that up and down the river valleys near here, up the Frome and Avon and Wellow Brook, you can find old pillbox forts still standing. Big pillboxes, with gun slits. Somewhat sinister looking things, crouching like huge armed toads, in the brambles near rivers. Why on earth would anyone want to build pillboxes on the Wiltshire-Somerset border?

To stop German tanks, I now learn from a fascinating booklet called Stop Line Green by Major Green (Reardon Publishing). In 1940, when the German tanks had swept across Europe, most people thought they would sweep across England next. Churchill thought this was a bad idea. So he ordered every possible obstacle to be put in the way of German tanks, and all through that summer a crash programme was put into operation to build anything that might slow down tanks beside natural obstacles such as the River Avon, or railway lines.

These pillboxes were thrown up in savage haste, says Major Green, but they were well and solidly built. I can testify to that. All the pillboxes near me are now camouflaged by dense bramble and elder trees, and are pretty smelly inside where they have been used as emergency refuges, but they should stand for at least another hundred years. There is a wood called Hog Wood near Hinton Charterhouse where I sometimes take the dog for a walk, and alongside the footpath there is a meandering ditch which I have always taken to be an old sunken way or perhaps a drainage gulley. Not so, I now learn. It is a genuine tank trap, dug in 1940, never used, never filled in and never forgotten, at least not by Major Green.

Strange, somehow, to wander among these relics of a campaign that never happened. The Major thinks that the line – built to safeguard Bristol – would probably have succumbed after the first breach, though the country would have been more favourable to defence against tanks in those days of many hedges and small fields. "It is now good tank country offering easy passage with wide and deep fields of view and fire." That is one thing I have never heard mentioned in debate about field usage – that the more hedges you grub out, the easier it is for tanks to come through.

By the end of summer 1940 the ring of defence called Stop Line Green (which linked up with others called Stop Line Blue and Red) was nearly ready. But by October we had won the Battle of Britain and a German invasion had become impossible. Churchill sent out an order: Forget about the Stop Lines – There Won't be Any German Tanks Coming. From that moment, the tank traps, pillboxes and tank bollards lay silent and forgotten, waiting for blackberries to grow on them and for their historian to come along. That man is Major Green (no first name, apparently) and his Stop Line Green, though only 36 pages long, is my military history of the year. Book of the year, probably.