Artifacts of the history of this area goes back to the Mesolithic age of about 8000 - 4000 BC. From this period over 6000 flint heads that were used for hunting and woodwork have been unearthed around the valley.
Excavations around Walton have revealed circular huts with hearths and pottery from the Neolithic or New Stone age of 4000 - 2000 BC. There were even traces of meat and dairy produce still on the fragments. On a more spectacular scale in 1994 aerial photography showed up crop marks revealing the presence of a large oval henge site enclosing 34 hectares now known as the Hindwell Palisade. Some 1400 post holes would have had oak trees 0.8m in diameter and 6m high. It is the largest site of this type in Britain although its exact purpose remains a mystery.

The Bronze age of 2000 - 800 BC left burial mounds called round barrows scattered in the valley and on the surrounding hilltops. In addition to these is the stone circle south of Kinnerton and other standing stones in nearby fields. Old Radnor church is built on a set of Bronze age earthworks.

The next inhabitants of this valley were more warlike than their predecessors and used iron. Their period spans roughly 800 BC - 41 AD when the Romans invaded Britain. Evidence of these turbulent times can be seen in the hillfort at Burfa and the enclosure at Castle Ring, both in defensive positions on top of hills at the eastern end of the valley. These people were known as the Deceangli

During the Roman period this region was part of the Empire's western frontier and five temporary, or marching camps have been identified around the Walton area. These relate to the various Roman campaigns that were undertaken against the local Deceangli tribe and the neighbouring Ordovices and Silures between 48 - 75 AD. The largest could accomodate up to 12000 men. During this period the old hillforts were attacked and destroyed. A permanent fort was built on a site near Hindwell Farm, probably during the 60's AD. Its typical shape can be seen from the air as crop marks adjacent to Hindwell farm.

After the departure of the Romans during the early 5th century the Angles and Saxons gradually spread westwards through Britain and this area once again became a frontier as can be discerned from the place names like Evenjobb, Kinnerton, Walton, Harpton and so on, which are all located down the valley behind a small Dyke called Ditchbank which can still be seen to the west of New Radnor. On the other side of this earthwork the place names are of Welsh origin. Along the eastern end of the valley runs the much larger-scale Offa's Dyke, constructed sometime in the second half of the 8th century demarking the kingdom of Mercia from its Welsh neighbours. It was probably built to protect Offas lands from reprisals by the Welsh after his various military campaigns and raids into Wales. This kind of behavior carried on through succesive Mercian and English kings right up to Harold Godwineson who temporarily conquered large areas of Wales prior to the Norman invasion of 1066. He is thought to have built a wooden castle at New Radnor in 1064 which was destroyed by the Welsh not long afterwards.

The period after the Norman invasion saw the construction of numerous small motte and bailey castles in the whole region. These were usually built with timber and some were developed further with stone over subsequent centuries. Many of the churches in the area were originally built during this period as the Normans utilised religeon as an equal instrument of control as their castles. No less than 10 castle sites have been identified in this small valley which shows that the area remained an uneasy and turbulent place, a situation that continued into the middle ages. The area was dominated by dynasties of Norman knights who had helped William the Conquerer in his invasion of Britain. These 'Marcher Lords' as they are known included the Mortimers and the Braoses who figure in much of the medieval history of these parts. Small towns called boroughs grew up to service some of the larger castles as can be seen at New Radnor. These would have been entirely populated by Normans and the language spoken was French. In the case of New Radnor town defences were also constructed and are still visible as earthworks. For over 300 years various attacks by the Welsh and inter-baronial feuds between the Marcher Lords ravaged these border lands and the general resentment felt by the Welsh since their domination by successive English kings came to culminate in the revolt led by Owain Glyndwr between 1400 - 1408. In this and earlier attacks New Radnor castle saw action, destruction and rebuilding, frequently being captured by one side or the other. This is known to have involved the slaughter of 60 of Edward Mortimers men in 1402. Human remains were descovered here in the 1970's, many decapitated and others with smashed spines.