Wargrave Local History Society’s January meeting was a well-illustrated presentation on Chalk, Caverns and Commandos by retired geophysicist Rob Wallace.
It was about the formation 94 million years ago of the chalk that lies below the Thames Valley, and the uses these deposits and the workings were put to in later times.
He explained that the time scales used by geologists are different to those in ‘normal’ use – to most people 1,000 years is a long time, but geologically it is ‘recent’, and ‘a million years’ is not very long for geologists.
The Thames Valley area was quite different 94 million years ago, with shallow warm water like the present Florida Keys.
Into the large areas of quite shallow relatively static water, layers of chalk were laid down, made of microscopic marine creatures forming millions of fossils which settled on the bottom eventually making significant thicknesses of chalk.
In the UK the oldest rocks are to the north and west, with younger ones to the south and east.
For the area to the south east of a line drawn from Flamborough Head, in Yorkshire, to the Dorset coast, the underlying strata is chalk, with younger rocks overlying the chalk in some areas and the local area (including Wargrave and Emmer Green) is on the upper chalk layer, formed when the area was a sub-tropical coastal marsh, and the chalk is very clean with very little grit or wood derived particles in it.
At the end of the Ice Age, water from melting glaciers spread a lot of material like gravels and clays, and iron oxide, some of which were left above the chalk.
Rob then told the history of how these were used locally. In Tudor times, brick making increased – using silica, clay, lime, iron oxide and magnesia which could all be found locally in the chalk or younger rocks above it, and Reading became famous therefore for their production – Thomas Hardy in Jude the Obscure calling Reading Aldbrickham – with the last brickworks staying in operation until 1967.
In the mid-Victorian era, a local brickworks could produce half a million bricks a year, but that represented only 100-200 houses, so Reading needed many such places.
One of the mines providing chalk for brick making was located at Milestone Wood, at Emmer Green, running under Kiln Road, with an extensive range of tunnels in the upper chalk strata. This is very white and clean with some layers of flint, about 20m below the surface.
Although the chalk is hard, miners working by candlelight could remove the rock using hammer and chisel without needing explosives – some of their tools being found in the tunnels.
There is no water in the mine – the tunnels being high above the river level.
As in many such caves, there is graffiti on the walls, the earliest date written there being 1776, the names including various notable Reading citizens.
In the late 1930s, it became obvious war would soon break out, and plans to save national treasures well away from possible enemy targets.
The ‘Peppard Road disused mine’ is mentioned as a place to store some National Archives and maybe Berkshire Archives.
Few people were needed to look after it, and it was safe from enemy bombs. Winston Churchill believed that auxiliary units of commandos would be necessary to fight a guerilla campaign against any invading forces, and is possible that a Nissen hut in the tunnels was for one of these units. They had modern armaments and supplies of explosives, intending to slow down an enemy advance.
Although there were a number of bases for auxiliary units, there is no formal record of where they were.
The brickworks associated with the mine appears to have ceased working during the 1950s, and the mine remained dormant for another 20 years or so, until the 89th Reading Scouts set about finding what lay beneath their Scout hut.
For more information about the society, or a more detailed report, visit the website at: www.wargravehistory.org.uk
PETER DELANEY
