Senghenydd was established as one of several administrative parts of the ancient South Wales kingdom of Dyfnefwr that was ruled by a 'prince'. They are described as comotes in Cronica Walliae. It has been suggested that the term comote dates from the end of the eleventh century as a political division that was applied to gatherings of neighbourhoods, previously known as cantrefs, that had grown too large to be administer individually. The comote of Senghenydd was situated for the most part between the valleys of the Taff and Rhymney (maked with purple lines in the following sketch map).

Sketch map of the territory of the comote
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The territory of Senghenydd was adminstered by a Welsh native prince in three divisions with a court at Merthyr Tudful, and possibly others at Senghenydd and Lisvane. The two northern territorial divisions are described in Cronica Walliae as Saynhenydd Uwchkaeach and Iskaeach; (Senghenydd above and below the River Caeach). The Caeach, although only a small river, cuts deeply into Senghenydd at Quakers Yard and provides the beginning of an west to east route across the comote from the Taff to the Rhymney valleys.

The southern part of the comote, known as Cibwr, extended from Caerffili Mountain to the mouth of the Taff. Cibwr was taken into the Fitzhamon Norman lordship of Cardiff when its administrative centre was established in the ruined Roman fort on the tidal Taff. What remained of Senghenydd north of Caerffili was administered by Welsh vassals until Cardiff and its coastlands was threatened by invasion from Brecon by Llywelyn the Great. Then the response of the Cardiff Normans was to build a castle at Caerffili and take over the entire comote. Henceforth, Caerffili was its military and manorial centre. This military response provides an indication of the strategic importance of Senghenydd to control an upland route from Cardiff into central Wales. That is to say, it was a legacy from times when the Roman port of Cardiff was connected via another fort at Gelligaer to Brecon. The fort at Gelligaer is positioned on the Senghenydd watershed and parts of the road can still be traced from Gelligaer as a ridgeway that runs north and south along the spine of the comote.

There is only one mapped place name of Senghenydd, and that refers to the old mining village at the head of the Aber Valley. The Aber is a tributary of the Rhymney, which it joins at a point where Caerffili now stands. The bottom of the Aber Valley has been occupied by the ribbon development of the colliery community of Abertridwr, which is almost continuous with the northern suburbs of Caerffili. Senghenydd and Abertridwr are hemmed in by a horshoe of mountain common land, about 300m high (Mynydd Eglwysilan, Cefn Eglwysilan, and Mynydd Meio). Before industrialisation of the valley the scattered farming community on the mountain side had its religious centres at Eglysilan (Church in Wales) and Groes-wen (Non-conformist). These are still small isolated upland communities. A unique feature of the commons is the system of 'dykes'. These are long cuts made a metre or so into the ground. They have been described as markers of commoners rights and attributed to the medieval period. However, there is no evidence, written or archeological, to verify this claim. The common land is all that remains of a much larger area, the lower slopes of which have been enclosed as fields to serve farmsteads. Field boundaries have been constructed in various ways. Some are made of dry stone walling, others are earthen banks planted with hawthorn or hazel, indicating that they may have been enclosed at different times.

Sketch map of the common lands of Senghenydd. Green lines represent positions of the Senghenydd 'dykes' as they appear on the current 1/25000 OS map.
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