the Southern edge of the Marlborough Downs, we encounter an odd feature in the landscape - a long, low earthwork, hugging the Downland scarp. You wouldn't notice it from the road unless you knew it was there.
This is Wansdyke. In all, it stretches from near Bristol to beyond Marlborough, though it disappears for long stretches in between.
It is a defensive ditch and rampart, extending for miles across Western England. But it's not at all clear who built it, or why.
The name comes from Woden's Dyke (Woden being the main god of the Saxons). This tells us that the Saxons themselves didn't build it - they came across it and treated it as an Act of God.
It bears some characteristics of a Roman military construction, but structure was built long after the legions left - about 600 A.D., perhaps. But then, the principles of Roman military tactics and construction survived the Imperial era by many centuries.
The current consensus is that Wansdyke was a Romano-Celtic artifact, built to hold back the encroaching Saxons - which would place it, roughly, in the Arthurian era.
The odd thing is that we have no documentary or traditional evidence for such a connection; a dyke like this would have taken extraordinary organisation and effort, and we would expect to find some celebrations of the achievement, or some legendary explanations for its appearance. But there's nothing.
Perhaps it failed to contain the Saxons, and the Celts quietly glossed over this embarrassing failure. The dyke was designed to defend against attacks from the North, but Wessex expanded into this territory from the South. Maybe the the Celts felt like prats - wasting all that effort on defenses which faced the wrong way.
On the other hand, Wansdyke might well have been built by Brits, to keep out other Brits; this was not a peaceful time. In such a case, the encroachment of Saxon armies might have rendered Wansdyke redundant.
A mile or so East of here, Wansdyke crosses Tan Hill (where there are some enclosures probably associated with the earthwork). Tan Hill (originally St. Anne's Hill) held an important sheep fair in mediæval times. Today it hosts kite and microlight flyers.
This stretch of Wansdyke forms a delightful walk on a sunny day - not too strenuous, good value for the effort.