This earthwork monument lying just east of the Brenig Reservoir has long been considered part of the Bishop of Bangor's estate at Llanrhaeadr in the Vale of Clwyd, whose pastures of Hiraethog came to be known as Bysshopeswall in the medieval period. By 1334 Bysshopeswall was an integral part of the lordship of Denbigh and it was stated in the Survey of the Honour of Denbigh that its 1127 acres could support 8 bulls and 192 cows throughout the year. It seems likely therefore that Hen Ddinbych originated as part of a vaccary or cattle ranch, primarily used during the summer months. The name Hen Ddinbych was applied to this monument in the 19th century, and prior to this it was simply known as hen dref (old settlement) or yr hen eglwys (the old church).

The monument is situated at the foot of a hillslope near the Aber Llech Daniel whose water would have provided an essential resource. It comprises a near square enclosure 82m wide by 92 long, delineated by a bank with outer ditch; the ditch acting as a drain to divert water running down the hillside and thus ensure a dry interior. Two entrances led into the enclosure one in the southeast corner and the second in the northwest corner, approached by a clearly defined hollow way. Within the southern half of the enclosure, are the stone foundations of a long and narrow building, most likely a barn (internally 32m long and 4m wide), with evidence of at least two entrances, one set in the end east wall and the other halfway along the north wall. This was constructed on a platform dug into the hillslope and links with a hollow way running to the entrance at the south-east corner of the enclosure. This arrangement is mirrored in the northern half of the enclosure where a similar platform has been dug into the hillslope, here however, there is no trace of a structure. An earthwork platform, 5m wide by 20m long also backs against the western enclosure bank and may have supported an additional structure, possibly a house to accommodate vaccary workers.

A detailed survey of the monument was carried by RCAHMW in 2009.

Louise Barker, RCAHMW, October 2010

Sources:
Davies, E. 1929. The Prehistoric and Roman Remains of Denbighshire, 313.
Gresham, C. & Hemp, W.J. 1959 Hen Ddinbych. Archaeologia Cambrensis vol. 108, 72-80