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Caersws Basin
Historic Landscape

Historic Landscape Characterisation

The Making of the Caersws Basin Landscape


The earliest political grouping known in the area is the native tribe known as the Ordovices who inhabited central Wales at the time of the Roman conquest in the 1st century AD.

There is no evidence for the establishment of civil administration during the period of Roman rule between the mid to late 1st century AD and the early 5th century and it is possible that the area continued to be subject to administration by the Roman army throughout this period.

It seems possible that by the early medieval period the area came to form part of the small kingdom or cantref of Arwystli, first recorded in the Domesday Book of 1086 (as the ‘hundred of Arvester’) whose name appears to be derived from a personal name.

During the earlier medieval period the small kingdom of Arwystli lay between and became a subject of violent disputes involving the two more powerful kingdoms of Gwynedd to the west and Powys to the east. Its early history is obscure though by the late 11th century it was held by the Norman earl, Roger de Montgomery, who had annexed the territory from his power base further east, but returned into the hands of a native dynasty during the first half of the 12th century. Arwystli continued to be hotly contested by the kings of Gwynedd and Powys for a period of about a century and a half during which much slaughter and destruction of buildings is recorded. Though much of the cantref was composed of no more than moorland it included some scarce, fertile valley land, especially in the valley of the river Severn and its tributaries, and was also of some strategic significance in terms of providing a corridor of communication between central Wales and the Marches. During this period allegiances ebbed and flowed between the local dynasty and the house of Gwynedd, the local dynasty and the house of Powys, between the house of Powys and the Crown of England, and even between the competing kingdoms of Gwynedd and Powys, until a period of relative stability following the conquest of Wales by Edward I in the 1280s when it reverted to Gruffudd ap Gwenwynwyn, the then ruler of Powys.

The historic landscape area formed the easternmost commote or administrative subdivision of the cantref, called Arwystli Iscoed (literally ‘Arwystli below the wood’) administered by stewards probably from the early 13th century. By the late 1290s Pen-prys in the parish of Llanwnog, now a farm known as Park about 2 kilometres to the west of Caersws, had become the manorial centre of Arwystli Iscoed. The two moated sites in the historic landscape area, The Moat and Rhos Ddiarbed, are set on the rising ground to the south of the valley, remote from early centres of population, and seem likely to represent relatively short-lived administrative centres associated with the campaigns of Roger de Montgomery in the late 12th century.

In later medieval times the commotal courts, the court leets for Arwystli Iscoed, were held alternately at Llandinam and Caersws, two of the principal centres of population in the area. The bishop of Bangor held significant lands in Llanwnog in the early 14th century, whose tenants were probably also subject to the jurisdiction of the episcopal court.

Arwystli together with the lordships of Cyfeiliog and Caereinion were regained by the Cherltons, lords of Powys in 1401, during the Glyndŵr uprising, from the prominent marcher lord Sir Edmund Mortimer who had formerly seized them. The lordship subsequently passed through the Tiptoft family to the Dudleys who sold the lordships to the Crown during the reign of Henry VIII.

At the Act of Union in 1536 the lordship of Arwystli was subdivided into manorial townships which had probably originated during early medieval and medieval times and which were to continue to have significance until the mid 19th century. Townships within the area bounded by the historic landscape comprise Escob and Castle, Wig (Weeg), Caersws and Surnant in the parish of Llanwnog, Trywythen, Carnedd, Gwerneirion, Maesmawr and Llandinam in the parish of Llandinam, Bodaeoch in the parish of Trefeglwys, and Penstrowed in the parish of Penstrowed.

Following the Act of Union the area became administered as part of Arwystli Hundred, subsequently renamed Llanidloes Hundred during the post-medieval period. It was divided into upper and lower divisions which loosely corresponded to the medieval commotes of Arwystli Uwchcoed and Iscoed. The Caersws Basin fell into the lower division, which included Llandinam, Llanwnog and Penstrowed parishes and part of Carno parish.

At the present day the historic landscape area falls largely within the communities of Caersws and Llandinam, but includes small parts of the communities of Mochdre and Aberhafesp. Following local government reorganisation in 1974 these communities fell within the newly-created county of Powys which became a unitary authority in 1996.

Ecclesiastical boundaries

The ecclesiastical parishes in the greater part of the area fall within the deanery of Arwystli in the diocese of Bangor, the only exception being a small area of the parish of Aberhafesp which falls within the diocese of St Asaph.

Two churches of medieval origin are known, at Llandinam and Llanwnog. Llandinam is the only one of the two listed as a church (ecclesia) in the Pope Nicholas taxation of about AD 1291. It was also a portionary church whose benefice was shared between a number of priests, which suggests that it probably originated as an early medieval clas foundation, a regionally important ecclesiastical centre, and together with Llangurig was one of the two mother-churches in Arwystli, one falling in each of the two commotes.

The status of Llandinam church in the later 13th century is emphasised by the figure of Cynyr ap Cadwgan, abbot of the clas at Llandinam, who was an authoritative compiler of Welsh law texts and founder of a dynasty of men learned in the law.

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