Mapping Mountains – Significant Name Changes – 100m Twmpau

Dinas Dinorwig (SN 549 652)

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips.

Dinas Dinorwig (SH 549 652)

The criteria for the list that this name change applies to are:

100m Twmpau - Welsh hills at or above 100m and below 200m in height with 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau with the criteria for this sub category being all Welsh hills at or above 100m and below 200m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

100m Twmpau by Myrddyn Phillips

The hill is adjoined to the Glyder Fawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is encircled by an old track to its north and minor roads to its west, south and east, with the B4366 road to its north-west and the A4244 road to its north-east, and has the small communities of Bethel towards the west, Rhiwlas towards the east and Llanrug towards the south-west.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill appeared under the transposed name of Pen Dinas, with an accompanying note stating; aka Dinas Dinorwig.

Pen Dinas

170m

SH549653

114/115

17/263

aka Dinas Dinorwig

During my early hill listing I thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day, with little consideration for the meaning of the name and where it was appropriately applied to.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance use what I thought was the name of the hill and which unbeknownst to me at the time, is the name of a farm.  This is not a practice that I now advocate as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found.

Extract from the Ordnance Survey 1:25,000 Explorer map

The summit of this hill has an ancient Iron Age Hillfort positioned on it which is known as Dinas Dinorwig, and it is this structure that gives its listed name to the hill, whereas although the name of Pen Dinas is evident on contemporary Ordnance Survey maps this name is that of a farm situated close to the summit and not the name of the hill itself.

The sign on the gate leading to Pendinas Farm

Therefore, as an appropriate name for the hill already exists on contemporary Ordnance Survey maps this hill is now listed as Dinas Dinorwig in the 100m Twmpau.

The full details for the hill are:

Group:  Glyder Fawr

Name:  Dinas Dinorwig

Previously Listed Name:  Pen Dinas 

OS 1:50,000 map:  114, 115

Summit Height:  169.8m (LIDAR)

Summit Grid Reference:  SH 54945 65256 (LIDAR)

Bwlch Height:  131.8m (LIDAR)

Bwlch Grid Reference:  SH 54642 64647 (LIDAR) 

Drop:  38.1m (LIDAR)

Myrddyn Phillips (March 2019)