NGRef: SN8231
OSMap: LR160
Type: Fortlet, Camp, Practice Work, Industry, Milestone
NW (5) to Llandovery (Llandovery, Dyfed)
ESE (12) to Y Gaer (Brecon Gaer, Powys)

Y Pigwn - 'The Beaks'

The Temporary Marching Camps at Y-Pigwn

Trecastle Marching Camps & Fortlet
Trecastle Marching Camps & Fortlet
Adapted from Haverfield (p.62 fig.22)

Two large, superimposed temporary marching camps lie to the north of the Roman road between Brecon and Llandovery (SN8231). Surrounding the summit of a 1,350 foot (412m) hill overlooking the Waun Ddu ("the Black Bog"), the larger encampment was evidently the first to be built, as the eastern corner-angle of the smaller camp - which lies almost entirely within the defences of the larger - partly overlies its south-eastern ramparts. The internal clavicula-type defences of both camps are indicative of an early construction date, perhaps Agricolan. The Powys / Dyfed regional border runs across the south-eastern corner of the site. Both camps are superbly represented on the 1891 map of Carmarthenshire (available online from; see below).

Y Pigwn Camp 1
SN828312 1,380 x 1,180 ft
(421 x 360 m)
37½ acres
(15 ha)
This, the larger of the two camps, has most of its perimeter recorded, with the exception of its northern and southern corner-angles; the positions of which may be easily inferred from the surviving defences. Two gateways are discernable, both protected by internal clavicula defences, one in the north-east rampart off-set to the north and another in the south-east defences off-set to the south on a ratio of 1:3. There are no traces of any gateways in either the north-west or south-west ramparts. It is possible that the camp was oriented towards the south-west. The camp's south corner-angle was overlain by the later Roman road.
Y Pigwn Camp 2
SN828312 1,190 x 930 ft
(363 x 283 m)
25½ acres
(10 ha)
This camp lies wholly within the perimeter of Camp-1 on a slightly different alignment. Almost the entire perimeter of the camp is known, with the exception of part of the south-eastern side. Three gateways are visible, all with traces of internal clavicula defences, set centrally in the north-east and south-west sides, and in the north-west side offset to the west by a ration of 2:3; the camp therefore faced ESE. The northern corner-angle overlies the clavicula defences of Camp-1, which must have been built first.

The Roman Practice Works at Cwm-y-Cadno

SN812314 114 x 114 ft
(c.34.7 x 34.7 m)
(c.0.12 ha)

A so-called 'military practice work' lies beside the Roman road in the valley below the fortlet; marked as a ROMAN CAMP on Landranger#160. This small camp is square in outline with rounded corners, each side measuring only 114 feet, and thus covering an area of just over ¼-acre (c.34.7 m, 0.12 ha). It has centrally-placed gateways 10 feet wide (c.3 m) protected by tutulus outworks in each side.

The Roman Fortlet on Mynydd Myddfai

SN821310 121 x 116 ft
(c.36.9 x 35.4 m)
c.0.32 acres
(c.0.13 ha)

Situated on a spur between two tributary streams of the Afon Gwydderig overlooking Hafod Fawr, about half a mile west of the Y-Pigwn marching camps, this small Roman fortlet was ideally placed to police the main Roman road between the forts at Brecon Gaer and Llandovery. The fortlet measures 121 feet from north-west to south-east, by 116 feet transversely within the ramparts (c.36.9 x 35.4 m), and encloses an area of just under one-third of an acre (c.0.13 ha) with a single rampart and ditch, 14 feet and 12 feet wide respectively (c.4.26 & 3.66 m). The Brecon road arrived outside the eastern defences of the fortlet and passed around its northern and western sides as it descended the steep incline of Trecastle Hill towards the Hafod Fawr practice works and Llandovery beyond. The fortlet is erroneously marked on OS Landranger Map#160 as a ROMAN FORT, and on Haverfield's map as an Outpost. After a considerable period of neglect the site was later used to house a Norman motte or 'castle mound' (called a tomen in Welsh), which occupies the northern corner of the site. The fortlet site is not recorded in RCAHMW Brecknock.

Roman Milestones from Trecastle Hill near Y-Pigwn

There are no inscriptions on stone recorded in Vol.I of the R.I.B. for any of the military encampments at Y Pigwn itself, but a couple of inscribed milestones or honorific pillars have been uncovered from Trecastle Hill near Hafod Fawr (SN8131), beside the Roman road to the immediate west of the fortlet.


"For the emperor, our lord [Caesar] Marcus Cassianius Latinius Postumus Pius Felix [Invictus] Augustus.¹"

(RIB 2260; milestone of Postumus; dated: 260-269AD; found with #2261)


"For Imperator Caesar Marcus Piavonius [Victorinus Pius Felix Invictus] Augustus.²"

(RIB 2261; milestone of Victorinus; dated: 269-271AD; found with #2260)

  1. The pseudo-emperor Postumus was the first ruler of the break-away Gallic Empire. The former Roman governor of Lower Germany revolted against the rule of the legitimate emperor Gallienus in the Autumn of 260AD following the death of the co-emperor Valerian on campaign in Persia. He was murdered by his own general Laelianus in February 269.
  2. Victorinus took control of the Gallic empire from Marius, after a two day interregnum, in Summer/Autumn 269AD. He ruled until early 271 when he was killed for making improper advances towards the wife of one of his generals. He was succeeded by Tetricus, who held the Gallic Empire together until early 274 when he and his like-named son were killed in battle near Trier by forces of the true Roman emperor Aurelian.

Other Sites of Interest in the Area

See: Chronicle of the Roman Emperors by Chris Scarre (Thames & Hudson, London, 1995);
R.C.A.H.M.W. - Brecknock (H.M.S.O. 1986) RMC1/2 pp.150-153 & figs.171-173;
The Roman Frontier in Wales by V.E. Nash-Williams (Cardiff 1969) p.124 & fig.66;
The Roman Inscriptions of Britain by R.G. Collingwood and R.P. Wright (Oxford 1965);
Air Reconnaissance in Britain, 1955-7 by J.K. St. Joseph in J.R.S. xlviii (1958) pp.95/6;
Air Reconnaissance of Southern Britain by J.K. St. Joseph in J.R.S. xliii (1953) p.86;
Military Aspects of Roman Wales by Prof. F. Haverfield (London 1910) pp.62/3;
All English translations, including any inherent mistakes, are my own.

Click here for a map of Y Pigwn from

Click here for a map of Y Pigwn from

Page Citation: Kevan White (2018) "Roman Britain: Y PIGWN"