Car Dyke
The Car Dyke is an 85-mile long ditch which runs along the western edge of the Fens in eastern England. The canal that runs down the east side of the Potterhanworth Woods is part of the Car Dyke. It can be traced for 52 miles from the River Witham at Washingborough to Peterborough, then follows the western edge of the Fens and possibly continues for a further 33 miles to the river Cam at Waterbeach in Cambridgeshire. This waterway dates back to Roman times. For much of its length it was and still is used for land drainage There is also evidence that parts of it were used as a canal for transporting goods and as a boundary marker.
Map tracing the route of the Car Dyke from the River Witham to Peterborough
The name Car Dyke appears in medieval times and may relate to a prominent landowner, Kari, or the old English ‘car’ which means wet scrubby woodland which the land on the fen-edge of the Dyke may well have been. Car Dyke is regarded by some to apply only to the section north of the River Nene with other names such as Cnut’s Dyke and The Old Tillage applying to parts of the southern section.
In Potterhanworth the Car Dyke functions as a catchwater drain; it intercepts water draining from the higher land to the west before it enters the low-lying fens. The water is directed to the River Witham along straight drains (called locally delphs) which prevents the fens becoming waterlogged and allows them to be productive farmland. It is likely to have served the same function in Roman times.
There is archaeological evidence that in Roman and medieval times parts of the Car Dyke were used as a canal to transport stone, pottery and coal. Excavations have shown an original navigable width of 12m and depth of 2m. It has been speculated that the Car Dyke may have also been used by the Romans to transport grain to supply garrisons in York and the north via the Fossdyke Canal (which runs from Lincoln to the Trent) which was also constructed in Roman times and is still in use. The Car Dyke however was not continuous so was unlikely to have been used for transport along its whole length.
An artist’s interpretation of how the Romans might have used the Car Dyke for transporting building materials
On the eastern bank of the Car Dyke, opposite Potterhanworth Woods and next to a footbridge, is a crude bench made of black wood. The wood is ‘bog oak’. It’s likely that thousands of years ago an oak tree fell close to this spot into a bog and was preserved by the acidic conditions. The timber is likely to be at least 3000 years old.
The dark fenland soil of the Witham Fen originated as peat in which are preserved the trunks of oak trees that grew here during a dry period in prehistoric times and are sometimes ploughed-up by farmers. Once the fen was drained, the peat that had accumulated in the wet conditions, dried out and decomposed. The shrinkage of the peat brought this and many more trees to the surface. These tree trunks are a hazard to farm equipment and they can be seen piled up on the side of black fen fields.
The Bog Oak Bench
The bench is made from the narrow end of the log. The log would have been 12m long and 1.2m diameter at the wide end. It was straight with only one branch and was found in the adjoining field. The tree must have grown in dense, high forest to be so tall and straight. The tree was unlikely to have grown so well in the waterlogged conditions that preserved the timber after it fell, indicating that the conditions got much wetter after the tree fell and stayed wet for thousands of years.
There is a short poem carved into the top of the bench:
“I grew here before the flood.
When wolf and aurochs walked the wood”
Aurochs were wild cattle, the ancestors of modern cattle, and were large and aggressive. They and wolves would have roamed the forest where the tree grew. The bench was made by Potterhanworth resident Nigel Sardeson in 2018.
Car Dyke Bridge - Barff Road c 1910