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)