Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales

Mynydd Margam (SS 819 888) – Pellennig deletion 

There has been a deletion to the listing of Y Pellennig – The Remotest 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 Aled Williams. 

LIDAR image of Mynydd Margam (SS 819 888)

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet and print-booklet version on Mapping Mountains Publications with the up-to-date master list available to download on the Mapping Mountains site in Google Doc format.

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Mynydd Margam, and it is adjoined to the Craig y Llyn group of hills, which are situated in the southern part of South Wales (Region B, Sub-Region B3), and it is positioned with the B4282 road to its north, the M4 motorway to its south-west and the A4063 road to its east, and has the town of Maesteg towards the north-east.

When the the Y Pellennig – The Remotest Hills of Wales was fiirst published in November 2011 on Geoff Crowder’s v-g.me website, this hill was listed with 2.500km of remoteness and with c 15m of drop, both of which are the minimum required for Pellennig status.

In April 2015 the list was published by Europeaklist in booklet format and by Haroldstreet and Mapping Mountains, with the list on the v-g.me website also updated.  The 2.500km remoteness and 15m drop were retained, with the latter based on the 344m summit spot height adjoined to a triangulation pillar that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and the 329m 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. 

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.

Therefore, the deletion of this hill from Pellennig status is due to LIDAR analysis, resulting in a 344.3m summit height and a 331.8m bwlch height, with these values giving this hill 12.5m of drop, which is insufficient for it to be classified as a Pellennig. 

 

The full details for the hill are: 

Group:  Craig y Llyn

Name:  Mynydd Margam

OS 1:50,000 map:  170

Summit Height:  344.3m (LIDAR)

Summit Grid Reference:  SS 81913 88854 (LIDAR)

Bwlch Height:  331.8m (LIDAR)

Bwlch Grid Reference:  SS 82342 88713 (LIDAR)   

Drop:  12.5m (LIDAR) 

Remoteness:  2.500km (no longer applicable)

 

For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:

 

Y Pellennig – The Remotest Hills of Wales

 

Aled Williams and Myrddyn Phillips (August 2026) 

Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales

Llethr Gwaered (SN 795 626) – Pellennig addition 

There has been an addition to the listing of Y Pellennig – The Remotest 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 Llethr Gwaered (SN 795 626)

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet and print-booklet version on Mapping Mountains Publications with the up-to-date master list available to download on the Mapping Mountains site in Google Doc format.

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Llethr Gwaered, and it is adjoined to the Drygarn Fawr group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B1), and it is positioned with a minor road to its north-west, and has the village of Pontrhydfendigaid towards the north-west.

When the original list that later became known as the Y Pellennig – The Remotest Hills of Wales was first compiled, this hill was not included with subsequent documentation giving it an estimated c 13m of drop, based on an estimated c 488m summit height based on interpolation of its uppermost 480m ring contour, and the 475m bwlch spot height that appears on the Ordnance Survey 1:25,000 Explorer map. 

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.

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 has a 489m summit spot height for this hill, and when coupled with the aforementioned 475m bwlch spot height, these values would give this hill 14m of drop. 

Extract from the interactive mapping hosted on the WalkLakes website

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.

Therefore, the addition of this hill to Pellenig status is due to LIDAR analysis, resulting in a 489.5m summit height and a 468.3m bwlch height, with these values giving this hill 21.2m of drop, which is insufficient for it to be classified as a Pellennig. 

The two Llethr Gwaered Pellennig summits; SH 795 626 and SN 801 625

Although this hill was originally unclassified, its adjacent 490m map heighted summit positioned at SN 801 625 was given Pellennig status.  As LIDAR gives this hill as 0.1m lower with 15.0m of drop compared to the summit of the hill positioned at SN 795 626, their respective bylchau are swapped and where there was just one listed Pellennig there are now two Pellennig hills. 

 

The full details for the hill are: 

Group:  Drygarn Fawr

Name:  Llethr Gwaered

OS 1:50,000 map:  147

Summit Height:  489.5m (LIDAR)

Summit Grid Reference:  SN 79564 62624 (LIDAR)

Bwlch Height:  468.3m (LIDAR)

Bwlch Grid Reference:  SN 79609 63025 (LIDAR)   

Drop:  21.2m (LIDAR) 

Remoteness:  3.800km (LIDAR)

 

For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:

 

Y Pellennig – The Remotest Hills of Wales

 

Aled Williams and Myrddyn Phillips (May 2026) 

Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales

Pt. 526.8m (SN 745 611) – Pellennig deletion 

There has been a deletion to the listing of Y Pellennig – The Remotest Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis conducted by Myrddyn Phillips and Aled Williams. 

Pt. 526.8m (SN 745 611)

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has 15m minimum drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet and print-booklet version on Mapping Mountains Publications with the up-to-date master list available to download on the Mapping Mountains site in Google Doc format.

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

The hill is being listed by the point (Pt. 526.8m) notation 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 and south, and has the small community of Pontrhydfendigaid towards the north-west and the town of Tregaron towards the west.

When the original list that later became known as the Y Pellennig – The Remotest Hills of Wales was first compiled, this hill was not included as with a 527m summit spot height and bwlch contouring between 510m – 520m that appear on the contemporary Ordnance Survey 1:25,000 Explorer map, interpolation gave this hill less than 15m of drop. 

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.

One of the resources recently available online is the mapping on the OS Maps website and the details for this hill were subsequently re-assessed against this mapping.  This is the replacement for OS Get-a-map and until recent times had contours at 5m intervals which were proving consistently more accurate compared to the 5m contours that sometimes appear on the Ordnance Survey 1:25,000 Explorer map and used to appear on the online Vector Map Local.  This mapping had bwlch contouring between 510m – 515m, with interpolation placing the height of the bwlch as an estimated c 511m, and when coupled with the 527m summit spot height these values gave this hill an estimated c 16m of drop, and therefore it was included as a Pellennig with 2.700km of remoteness. 

Extract from the interactive mapping that was hosted on the OS Maps website

The hill was subsequently surveyed with the Trimble GeoXH 6000, resulting in a 526.8m summit height and a 511.9m bwlch height.  Although this survey gave this hill 14.9m of drop, it was decided that the bwlch position was incorrect and therefore the hill was retained as a Pellennig. 

The Trimble GeoXH 6000 gathering data at the summit of Pt. 526.8m (SN 745 611)

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 Pt. 526.8m (SN 745 611)

Therefore, the deletion of this hill from Pellenig status is due to a Trimble GeoXH 6000 summit survey and LIDAR bwlch analysis, resulting in a 526.8m summit height and a 512.0m bwlch height, with these values giving this hill 14.8m of drop, which is insufficient for it to be classified as a Pellennig. 

 

The full details for the hill are: 

Group:  Esgair Wen

Name:  Pt. 526.8m

OS 1:50,000 map:  146, 147

Summit Height:  526.8m (Trimble GeoXH 6000)

Summit Grid Reference:  SN 74595 61119 (Trimble GeoXH 6000)

Bwlch Height:  512.0m (LIDAR)

Bwlch Grid Reference:  SN 74980 61422 (LIDAR)   

Drop:  14.8m (Trimble GeoXH 6000 summit and LIDAR bwlch) 

Remoteness:  2.700km (no longer applicable)

 

For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:

 

Y Pellennig – The Remotest Hills of Wales

 

Aled Williams and Myrddyn Phillips (November 2023) 

Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales

Twll y Gwyddel (SM 705 225) – Pellennig addition

There has been an addition to the listing of Y Pellennig – The Remotest Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Aled Williams.

Twll y Gwyddel (SM 705 225)

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on the Mapping Mountains site in Google Doc format.

This hill is a stack and it is found in Twll y Gwyddel and is adjoined to the Carn Llidi group of hills which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and it is positioned with the southern part of Ynys Dewi to its north and Ynys Cantwr to its south.

This hill was not included when the original list of Pellennig hills was compiled as contemporary Ordnance Survey 1:25,000 Explorer maps do not give it any contour ring.  The lack of contour rings is also applicable to the Ordnance Survey Vector Map Local hosted on the Geograph website which is entitled the Interactive Coverage Map.

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

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

The details for this area were re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has 5m contour intervals.  But even this map does not show this hill as having any contour rings.

Extract from the OS Maps website

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 DSM image of the stack found in Twll y Gwyddel.  1m contour (black), 10m contour (red) and sea level (yellow).

LIDAR DSM image of the stack found in Twll y Gwyddel.  Black lines represent 1m contours, yellow lines represent sea level below which is coloured dark blue.  Coloured shading represents land between 1m contours.  Red line denotes the valley-to-valley traverse through the boulders which are found between the stack and Foel Fawr to the north

The addition of this hill to Pellennig status is due to LIDAR analysis, resulting in a 16.4m summit height and a 0.8m bwlch height, with these values giving this hill 15.6m of drop, and with the distance between its summit and the nearest paved public road being 3.300km, it gives this hill sufficient remoteness and drop for Pellennig status.

The full details for the hill are:

Group:  Carn Llidi

Name:  Twll y Gwyddel

OS 1:50,000 map:  157

Summit Height:  16.4m (LIDAR)

Summit Grid Reference:  SM 70552 22500 (LIDAR)

Bwlch Height:  0.8m (LIDAR)

Bwlch Grid Reference:  SM 70545 22512 (LIDAR)  

 

Drop:  15.6m (LIDAR)

Remoteness:  3.300km

For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:

Y Pellennig – The Remotest Hills of Wales

Myrddyn Phillips and Aled Williams (July 2019)

© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.

Mapping Mountains – Hill Reclassifications – Y Pellennig – The Remotest Hills of Wales

Pt. 22.2m (SM 701 226) – Pellennig addition

There has been an addition to the listing of Y Pellennig – The Remotest Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill confirmed by LIDAR analysis conducted by Aled Williams.

Pt. 22.2m (SM 701 226)

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

Y Pellennig – The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop, the list is a joint compilation between Myrddyn Phillips and Aled Williams and is available as a downloadable e-bookletor print-booklet version on Mapping Mountains Publications with the up-to-date master list available on the Mapping Mountains site in Google Doc format.

As the authors do not know an appropriate name for this hill either from historic research or local enquiry it is being listed by the point (Pt. 22.2m) notation, and it is adjoined to the Carn Llidi group of hills which are situated in the south-western part of Mid and West Wales (Region B, Sub-Region B4), and it is positioned in a small sheltered bay on the southern side of Ynys Dewi.

This hill was not included when the original list of Pellennig hills was compiled as contemporary Ordnance Survey 1:25,000 Explorer maps do not give it any contour ring.  The lack of contour rings is also applicable to the Ordnance Survey Vector Map Local hosted on the Geograph website which is entitled the Interactive Coverage Map.

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

Extract from the Ordnance Survey Vector Map Local hosted on the Geograph website

The details for this hill were re-assessed when the OS Maps website became available online.  This is the replacement for OS Get-a-map and has 5m contour intervals.  This mapping gives this hill an uppermost 15m ring contour, but as this hill is adjoined to its southerly counterpart which is already listed as a Pellennig hill by a connecting bwlch higher than 5m it implies that its drop is less than the minimum 15m required for it to be considered for Pellennig status.

Extract from the OS Maps website

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 Pt. 22.2m; 1m contour (black), 10m contour (red) and sea level (yellow)

Close up LIDAR image of Pt. 22.2m; 1m contour (black), 10m contour (red) and sea level (yellow)

The addition of this hill to Pellennig status is due to LIDAR analysis, resulting in a 22.2m summit height and confirmation that this is also its drop value as the connecting bwlch is below sea level, and with the distance between its summit and the nearest paved public road being 3.400km, it gives this hill sufficient remoteness and drop for Pellennig status.

The full details for the hill are:

Group:  Carn Llidi

Name:  Pt. 22.2m

OS 1:50,000 map:  157

Summit Height:  22.2m (LIDAR)

Summit Grid Reference:  SM 70180 22696 (LIDAR)

Bwlch Height:  N/A, sea level

Bwlch Grid Reference:  N/A, sea level 

  

Drop:  22.2m (LIDAR)

Remoteness:  3.400km

For the additions and deletions to Y Pellennig – The Remotest Hills of Wales reported on Mapping Mountains please consult the following Change Register:

Y Pellennig – The Remotest Hills of Wales

Myrddyn Phillips and Aled Williams (June 2019)

© Crown: CHERISH PROJECT 2019. Produced with EU funds through the Ireland Wales Co-operation Programme 2014-2020. All material made freely available through the Open Government Licence.