Mapping Mountains – Significant Name Changes – The Fours – The 400m Hills of England

Disgwylfa (SO 172 841)

There has been a Significant Name Change to a hill that is listed in The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Disgwylfa (SO 172 841)

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

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The hill is adjoined to the Cilfaesty group of hills, which are situated adjoined to the Welsh border, and it is positioned with the B4368 road to its north, and minor roads to its west and east, and has the town of Ceri towards the north north-west.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop.

Prior to this revision this hill was provisionally listed under the name of Bettws Hill Wood, which is a prominent name that appears near its summit on the Ordnance Survey 1:25,000 Explorer map, with an estimated c 15m of drop, based on the 427m summit spot height positioned at SO 17503 84053 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 412m col height, based on interpolation of 10m contouring between 410m – 420m. 

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

Since the original compilation of this list 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.  Two of the historic maps now available online are the Ordnance Survey Draft Surveyors map which formed the basis for the first publicly available Ordnance Survey One-Inch ‘Old Series’ map, and it is the latter map that has prompted the change in the listed name of this hill.

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 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 places the name Disgwylfa adjacent to the summit of this hill. 

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

Therefore, the name this hill is now listed by in The Fours – The 400m Hills of England is Disgwylfa, and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map. 

 

The full details for the hill are:

Group:  Cilfaesty

Name:  Disgwylfa

Previously Listed Name:  Bettws Hill Wood

OS 1:50,000 map:  136

Summit Height:  428.9m (LIDAR)

Summit Grid Reference:  SO 17246 84195 (LIDAR)

Col Height:  410.9m (LIDAR)

Col Grid Reference:  SO 17775 83941 (LIDAR)

Drop:  18.0m (LIDAR)

 

Myrddyn Phillips and Aled Williams (March 2026) 

Mapping Mountains – Significant Height Revisions – Y Pedwarau – The 400m Hills of Wales

 

Bryn Berw (SN 714 505)

There has been a Significant Height Revision to a hill that is listed in the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Bryn Berw (SN 714 505)

The criteria for the list that this height revision applies to are:

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills, with this hill being included in the 400m Sub-Pedwar category.  The criteria for this sub category being all Welsh hills at or above 400m and below 500m in height that have 20m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Bryn Berw, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north-east and west, and has the village of Llanddewibrefi towards the north-west.

When the original 400m height band of Welsh P30 hills was published on Geoff Crowder’s v-g.me website, this hill was included in the accompanying Hills to be surveyed sub list with a non-interpolated 430m summit height. 

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

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 28m of drop, based on the 433m summit spot height and the 405m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.  And these are the details the hill was listed by when the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013.

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR summit image of Bryn Berw (SN 714 505)

LIDAR analysis gives the highest ground on this hill as 430.7m positioned at SN 71433 50501, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 430.7m and this was derived from LIDAR analysis, this is 2.3m lower than the previously listed summit height, which was based on the 433m spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Esgair Wen 

Name:  Bryn Berw 

OS 1:50,000 map:  146, 147

Summit Height (New Height):  430.7m (LIDAR) 

Summit Grid Reference:  SN 71433 50501 (LIDAR) 

Bwlch Height:  403.3m (LIDAR) 

Bwlch Grid Reference:  SN 71373 50607 (LIDAR) 

Drop:  27.4m (LIDAR)

 

Myrddyn Phillips and Aled Williams (March 2026)

Mapping Mountains – Hill Reclassifications – The Welsh P15s

Twyni Mawr (SN 606 938) – Welsh P15 addition 

There has been an addition to the list of The Welsh P15s, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

Twyni Mawr (SN 606 938)

The criteria for the list that this addition applies to are:

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Twyni Mawr, and it is adjoined to the Banc Llechwedd Mawr group of hills, which are situated in the north-western part of South Wales (Region B, Sub-Region B1), and it is positioned with the coast to its west, a minor road to its east and the B4353 road to its south-east, and has the village of Y Borth towards the south.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in either the main list or the accompanying sub list, as with no significant contours of note on the contemporary Ordnance Survey 1:25,000 map, it was hard to know whether any hill with qualifying prominence existed. 

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

Since the compilation of The Welsh P15s first started 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 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.

One of the mapping resources now available online is the WalkLakes website which hosts an interactive map originated from the Ordnance Survey Open Data programme.  This map has many spot heights not on other publicly available maps and for this hill a 20m uppermost contour is shown. 

Extract from the interactive mapping hosted on the WalkLakes website

Another resource now available online is the interactive mapping hosted on the Welsh Government website and entitled the DataMapWales.  This mapping has 5m contours and its detail matches that produced from the OS Terrain 5 product, which compliments much of that produced from LIDAR, and for this hill there are two 23m spot heights shown. 

Extract from the DataMapWales

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales. 

LIDAR image of Twyni Mawr (SN 606 938)

Therefore, the addition of this hill to Welsh P15 status is due to LIDAR analysis, resulting in a 22.8m summit height and a 4.4m bwlch height, with these values giving this hill 18.4m 0f drop, which is sufficient for it to be classified as a Welsh P15. 

 

The full details for the hill are: 

Group:  Banc Llechwedd Mawr 

Name:  Twyni Mawr 

OS 1:50,000 map:  135

Summit Height:  22.8m (LIDAR)                                                           

Summit Grid Reference:  SN 60614 93828 (LIDAR)                                                  

Bwlch Height:  4.4m (LIDAR) 

Bwlch Grid Reference:  SN 60576 92484 (LIDAR) 

Drop:  18.4m (LIDAR) 

 

Myrddyn Phillips (March 2026) 

Mapping Mountains – Significant Name Changes – 200m Twmpau

 

Chwarel Penrhyn (SH 621 658) 

There has been a Significant Name Change to a hill that is listed in the 200m 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. 

LIDAR image of Chwarel Penrhyn (SH 621 658)

The criteria for the list 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.  The list is authored by Myrddyn Phillips, with the word Twmpau being an acronym standing for thirty welsh metre prominences and upward. 

200m 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 positioned with the B4409 road to its north, a minor road to its west and the A5 road to its east, and has the town of Bethesda towards the north-east.

When the original 200m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the accompanying Hills to be surveyed sub list, as with no significant contours of note on the contemporary Ordnance Survey 1:25,000 map, it was hard to know whether any hill with qualifying prominence existed and therefore it was considered not to meet the criteria then used for this sub category. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR analysis gives this hill a 220.6m summit height and a 197.0m bwlch height, with these values giving this hill 23.6m of drop and therefore it qualifies for 200m Sub-Twmpau status and was provisionally listed under the name of Penrhyn Slate Quarry, which is a prominent name that appears adjacent to the hill on the contemporary Ordnance Survey 1:25,000 Explorer map.

The intricacies of language and prioritising one in favour of another for listing a hill is fraught with complication, with originating Cymraeg names being anglicised and also originating English names being cymricised, examples such as these are more common in border country and especially so for anglicised forms.  There is no steadfast rule that fits all, but as a standard a name that has its origins in the Welsh language and where this is substantiated by either historic documentation and/or contemporary usage should be prioritised in favour of a contemporary anglicised or English version of the name.  Likewise, if a name exists where an element of it is in English and if this name applies to a hill that is situated in a Welsh speaking part of Wales it is standard practice to use a full Welsh term for the name.  It is also standard practice to use a Welsh name for a hill if another name exists that has originated in a different language.

Therefore, the name this hill is now listed by in the 200m Twmpau is Chwarel Penrhyn, and this was derived from the Ordnance Survey 1:25,000 Explorer map, with the language protocol also being used. 

 

The full details for the hill are:

Group:  Glyder Fawr

Name:  Chwarel Penrhyn

Previously Listed Name:  Penrhyn Slate Quarry   

OS 1:50,000 map:  115

Summit Height:  220.6m (LIDAR) 

Summit Grid Reference:  SH 62149 65875 (LIDAR) 

Bwlch Height:  197.0m (LIDAR) 

Bwlch Grid Reference:  SH 61793 65966 (LIDAR) 

Drop:  23.6m (LIDAR) 

 

My thanks to Aled Williams for advice relating to the listed name of this hill 

Myrddyn Phillips (March 2026)

Mapping Mountains – Summit Relocations – The Fours – The 400m Hills of England

 

Disgwylfa (SO 172 841) 

There has been a Summit Relocation to a hill listed in the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Disgwylfa (SO 172 841)

The criteria for the list that this summit relocation applies to are:

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is now listed by is Disgwylfa, and this was derived from the Ordnance Survey One-Inch ‘Old Series’ map, and it is adjoined to the Cilfaesty group of hills, which are situated adjoined to the Welsh border, and it is positioned with the B4368 road to its north, and minor roads to its west and east, and has the town of Ceri towards the north north-west.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop.

Prior to this revision this hill was listed with an estimated c 15m of drop, based on the 427m summit spot height positioned at SO 17503 84053 that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 412m col height, based on interpolation of 10m contouring between 410m – 420m. 

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

However, it was not until LIDAR became available that the details for this hill could be accurately re-assessed.  The LIDAR (Light Detection & Ranging) technique produced highly accurate height data that is now freely available for much of England and Wales.

LIDAR analysis gives the highest ground on this hill as 429.2m positioned at SO 17249 84185.  However, this is to the top of a raised track that forms a field boundary and protocols dictate that as this is deemed a relatively recent man-made construct such ground is discounted from the height of a hill. 

LIDAR summit image of Disgwylfa (SO 172 841)

The height produced by LIDAR analysis to the natural summit of this hill is 428.9m and this is positioned at SO 17246 84195, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or the de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the summit height produced by LIDAR analysis is 428.9m and this is positioned at SO 17246 84195.  This position is not given a spot height on the contemporary Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and is approximately 10 metres north north-westward from where the high point of the raised track that forms a field boundary is positioned and approximately 263 metres west north-westward from where the 427m spot height appears. 

 

The full details for the hill are:

Group:  Cilfaesty

Name:  Disgwylfa

OS 1:50,000 map:  136

Summit Height:  428.9m (LIDAR)

Summit Grid Reference (New Position):  SO 17246 84195 (LIDAR)

Col Height:  410.9m (LIDAR)

Col Grid Reference:  SO 17775 83941 (LIDAR)

Drop:  18.0m (LIDAR)

 

Myrddyn Phillips and Aled Williams (March 2026)