Mapping Mountains – Significant Name Changes – 200m Twmpau and Y Trechol – The Dominant Hills of Wales

 

Llethr Llwyd (SN 616 346) 

There has been a Significant Name Change to a hill that is listed in the 200m Twmpau and Y Trechol – The Dominant Hills of Wales, with the summit height, bwlch height and their locations, the drop, dominance and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Llethr Llwyd (SN 616 346)

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

200m Twmpau – Welsh hills at or above 200m and below 300m in height that have 30m minimum drop, with an accompanying sub list entitled the 200m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 200m and below 300m in height with 20m or more and below 30m of drop, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

The 200m Twmpau by Myrddyn Phillips

Y Trechol – The Dominant Hills of Wales – Welsh P30 hills whose prominence equal or exceed half that of their absolute height.  With the criteria for Lesser Dominant status being those additional Welsh P30 hills whose prominence is between one third and half that of their absolute height.  The list is authored by Myrddyn Phillips with the Introduction to the start of the Mapping Mountains publication of this list appearing on the 3^rd December 2015, and the list is now available in its entirety on Mapping Mountains in Google Doc format. 

Y Trechol - The Dominant Hills of Wales by Myrddyn Phillips

The hill is adjoined to the Mynydd Pencarreg group of hills, which are situated in the south-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the B4337 road to its north, the B4310 road to its west and the B4302 road to its east, and has the village of Llansawel towards the north.

The hill appeared in the original Welsh 200m P30 list on Geoff Crowder’s v-g.me website, under the transposed name of Banc Beili-Tew, which is a prominent name that appears just to the north of the summit of this hill on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map.

Banc Beili-Tew

278m

SN616346

146

186

Clem/Yeaman. Trig pillar.

 

During my early hill listing I paid little regard to name placement on the map, or the meaning of names and to what feature the name was appropriately applied to.  Therefore, I prioritised names for listing purposes that I now understand are either inappropriate or where another name is viewed as being more appropriate. 

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

Since the original publication of the Welsh P30 lists on Geoff Crowder’s v-g.me website there have been a number of maps made available online.  Some of these are historic such as the series of Six-Inch maps on the National Library of Scotland website.  Whilst others were digitally updated such as the Ordnance Survey Vector Map Local that was hosted on the Geograph website and which was entitled the Interactive Coverage Map, whilst others are current and digitally updated such as the interactive mapping on the Magic Maps and WalkLakes websites, and it is the series of Six-Inch maps that were consulted for name placement in relation to this hill. 

Extract from the Ordnance Survey series of Six-Inch maps

The Ordnance Survey series of Six-Inch maps formed the base map Ordnance Survey used for many decades leading to the production of the 1:10,000 series of maps, both have now been superseded by the digitised Master Map.  The series of Six-Inch maps are excellent for name placement and especially so compared to the contemporary Ordnance Survey 1:25,000 Explorer map, and it is the series of Six-Inch maps that give the name of Llethr Llwyd in relation to this hill with that of Banc Beili Tew applying to land to its north.

Therefore, the name this hill is now listed by in the 200m Twmpau and Y Trechol – The Dominant Hills of Wales is Llethr Llwyd, and this was derived from the contemporary Ordnance Survey 1:25,000 Explorer map with its placement substantiated from the Ordnance Survey series of Six-Inch maps. 

 

The full details for the hill are:

Group:  Mynydd Pencarreg

Name:  Llethr Llwyd

Previously Listed Name:  Banc Beili-Tew   

OS 1:50,000 map:  146

Summit Height:  277.9m (LIDAR) 

Summit Grid Reference:  SN 61605 34623 (LIDAR) 

Bwlch Height:  157.0m (LIDAR) 

Bwlch Grid Reference:  SN 60206 35153 (LIDAR) 

Drop:  120.9m (LIDAR) 

Dominance:  43.52% (LIDAR) 

 

Myrddyn Phillips (June 2022)