TWYN Y Gaer is an Iron Age British hill-fort which lies in the Black Mountains at the southern end of the long ridge between the valley of the Grwyne Fawr and the Vale of Ewyas.

Several public footpaths and green lanes weave their way around the lower slopes and the upper part of the hill is designated as open country and freely accessible to walkers.

The old camp itself is a strongly embanked and ditched enclosure which occupies the impressive summit of an isolated and dramatic hill.

It is roughly oblong in shape divided by two cross ditches into three compartments; it encloses an area of fourand-a-half acres and commands views of three valleys.

There is a single concave east-facing entrance. The picture here shows a reconstruction of the east gate at the approach our walk takes to the summit.

There were steep and bold entrenchments, which were widened and hollowed out at the entrance so as to accommodate defenders who would protect the fort at close quarters.

They can be thought of as “bow-andarrow pits”.

The northern rampart is clearly defined and offered protection on the naturally weakest side.

On the southern side facing Sugar Loaf and Bryn Arw, the rampart is understandably much less formidable, given how sharply the hillside drops away to the farmland below.

This fort at Twyn y Gaer was the central one of three, all guarding the southern approaches to the Black Mountains. The others were Crug Hywel on Table Mountain, four miles to the west at Crickhowell; and Pentwyn, two miles to the east on the southern tip of Hatterall Ridge.

It is almost certain from the remains of hut platforms and the range of domestic Iron Age objects found during excavations that the site was permanently inhabited. Finds include pottery, salt containers, and brooches.

The economy was mixed, with stone mills for grinding corn indicating cereal cultivation, and iron slag and crucibles suggesting some form of iron working.

Glass beads dating from fourth to first centuries BC have also been discovered at Twyn y Gaer.

They resemble others found at Iron Age female burial sites, and the inhabitants may have worn them as necklaces or pendants.

Some of the finds which date to the earlier phases point to cultural links with the tribe of mid-Wales and Herefordshire.

But towards the first century BC it would appear that the main influence came from the tribe located to the south, known to the Romans as the Silures.

The Silures lived in well-defended hill forts, were skilled at attacking their enemies when they were least expecting it, and they put up redoubtable resistance to the Romans.

According to the historian Tacitus's biography of Agricola, who was responsible for much of the Roman conquest of Britain, the Silures usually had a dark complexion and curly hair. Due to this appearance, Tacitus hinted that they may have crossed over from Spain at an earlier date.

Twelve centuries after the departure of the Silures, work began on a place of worship at Cwmyoy in the Vale of Ewyas which has become known as “the most crooked church in Great Britain”.

Lying on top of clay and limestone, the Old Red Sandstone ground had not finished settling when the church was built. Down the centuries, the building has been twisted in all directions by subsidence and the tower and chancel have moved in opposite directions. St Martin’s now perches precariously at an angle greater than that of the Leaning Tower of Pisa.

Undertake this excellent moorlandtype walk and you can train your sights on the lop-sided church from Twyn Y Gaer. If you feel the inclination…