Tuesday 3 March 2020

Mapping Mountains – Significant Name Changes – 100m Twmpau and Y Trechol – The Dominant Hills of Wales


Castle Park (SO 381 021)

There has been a Significant Name Change to a hill that is listed in the 100m Twmpau and the Y Trechol – The Dominant Hills of Wales, with the summit height and its location confirmed by LIDAR analysis conducted by Myrddyn Phillips, and the bwlch height and its location, the drop and status of the hill derived from detail on contemporary Ordnance Survey maps.

LIDAR image of Castle Park (SO 381 021)

The criteria for the two listings 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, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward.

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, with the Introduction to the Mapping Mountains publication of this list appearing on the 3rd December 2015, and which is now available in its entirety on Mapping Mountains in Google Doc format.

The hill is adjoined to the Mynyddoedd Duon group of hills which are situated in the eastern part of South Wales (Region C, Sub-Region C3), and it has the Afon Wysg (River Usk) and the B4598 road to its west, the A472 road to its south and minor roads to its east and north, and has the town of Brynbuga (Usk) towards the south-west.

The hill originally appeared in the 100m P30 list on Geoff Crowder’s v-g.me website under a partly transposed name of Lady Hill, with an accompanying note stating; Name from wood to the North-West.


Lady Hill110mSO382022171152Trig pillar. Name from wood to the North-West.


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.  My preference was to use farm names and put Pen, Bryn or Moel in front of them or as in this instance transpose the name of near wood and exclude the word Wood from it.  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 publication of these P30 lists on Geoff Crowder’s v-g.me website there have been a number of Ordnance Survey 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 are current and digitally updated such as the Vector Map Local hosted on the Geograph website and which is entitled the Interactive Coverage Map.  One of the historic maps now available is the Ordnance Survey One-Inch ‘Old Series’ map and it is this map that formed the basis for the change in this hill’s listed name.

Extract from the Ordnance Survey One-Inch 'Old Series' map

The One-Inch ‘Old Series’ map was the first map that Ordnance Survey produced, and their publication culminated from the whole of Britain being surveyed between 1791 and 1874 and the detail gathered therein produced at a scale of one inch to the mile and published in sheet format between 1805 and 1874.  The One-Inch ‘Old Series’ maps for the whole of Wales are now available online; they are also available in map format as enlarged and re-projected versions to match the scale and dimensions of the Ordnance Survey 1:50,000 Landranger series and are published by Cassini.  This series of maps form another important part in the study of Welsh upland place-names and bridge the timeframe leading up to the production of the Ordnance Survey base map of the Six-Inch series, and importantly for this hill and its listed name, it is this map that names the area taking in the hill as Castle Park.

Therefore, the name this hill is now listed by in the 100m Twmpau and Y Trechol – The Dominant Hills of Wales is Castle Park, and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map.


The full details for the hill are:

Group:  Mynyddoedd Duon

Name:  Castle Park

Previously Listed Name:  Lady Hill

OS 1:50,000 map:  171

Summit Height:  110.0m (LIDAR)

Summit Grid Reference:  SO 38199 02145 (LIDAR)

Bwlch Height:  c 67m (interpolation)

Bwlch Grid Reference:  SO 38974 02847 (interpolation) 

Drop:  c 43m (LIDAR summit and interpolated bwlch)

Dominance:  39.07% (LIDAR summit and interpolated bwlch)


Myrddyn Phillips (March 2020)



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