News from ACORN

Arlesey Conservation For Nature

A Brief History of Living on the Arlesey Sea Bed

Much has been made recently of the importance of preserving our rivers. Arlesey has three main water courses and is partly surrounded by them. The River Hiz on the west, the River Ivel on the north, and coming across on the north east side we have the Pix Brook. The Ivel and Hiz have been victims over the years of over abstraction of water at their well heads. This danger to the River Hiz was recognised a few years ago and pumping from its Oughton Head source was ceased. The debate about the Ivel is still ongoing. The Pix Brook suffered from contamination from the Letchworth Sewage Works for many years but fortunately that is no more. Water, especially clean water, is important to communities and many grew along rivers both being a source of food and a highway. So how did we come to have these rivers? Three quarters of a million years ago Arlesey was at the bottom of the sea or rather at the bottom of the Great Bytham River. Examination of the ground geology proves this by a rich layer of river alluvium deposits which gives us chalk, clay and gravel. This is why there are an abundance of disused clay pits and gravel pits all around the village and also one large chalk pit (the Blue Lagoon) which provided material for making cement.

Proof of us living on a sea bed can be found deep in the chalk as chalk is made from the gradual accumulation of minute marine calcite shells. Fossilised remains can be found of some larger shells (See illustration below) of the molluscs that lived in the bottom of the ‘Arlesey’ sea.

To give you some indication of the size of the Great Bytham River, the northern bank was in Lincolnshire and went across the Midlands to Warwickshire, touching Derbyshire and the southern bank somewhere down here in Cambridgshire and Bedfordshire. Even two thousand years ago around the time of Jesus of Nazareth, the area was still nothing like we have today. A thousand years later the Arlesey area was nothing but a large swamp. At that time it was inhabited by the Saxon Gifla tribe led by Alfric. When The Danes arrived from the North Sea the rivers were still very navigable. Barges brought coal and took vegetables between Newcastle and Shefford via the River Ouse at the Wash.

If you would like to grasp a bigger insight of that period then Francis Pryor of Time Team fame paints a larger picture in his book the “The Fens: Discovering England's Ancient Depths” . ACORN is not about history but is about preserving what we have left of the natural environment today. Remember most of what is left today is manmade. Vast acres of the land are now fast disappearing under housing and the polluted water runoff will end up in our local streams.

We hope this article was not too dry and dusty, but understanding the past and what happened gave us what we have today and gives us the knowledge to preserve what we have now.

If you would like to help maintain this legacy you can contact ACORN via their email address at

acorn.arlesey@ntlworld.com