Mapping Mountains – Hill Reclassifications – 200m Twmpau

Brimford Wood (SJ 304 144) – 200m Sub-Twmpau addition

There has been confirmation of an addition of a hill to the list of 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 Brimford Wood (SJ 304 144)

The criteria for the list that this addition 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 name the hill is listed by is Brimford Wood, and it is adjoined to the Stiperstones group of hills, which are situated in the north-eastern part of South Wales (Region B, Sub-Region B2), and it is positioned encircled by minor roads, with the B4393 road farther to its north-east, the A483 road farther to its west and the A458 road farther to its south, and has the small community of Crew Green 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 it was considered not to meet the criteria then used for this sub category.

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 an estimated c 21m of drop, based on an estimated c 258m summit height and an estimated c 237m bwlch height, with both heights based on interpolation of 5m contouring that appear on the Ordnance Survey 1:25,000 Explorer 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 confirmation of the addition of this hill to 200m Sub-Twmpau status is due to LIDAR analysis, resulting in a 258.3m summit height and a 236.2m bwlch height, with these values giving this hill 22.1m of drop, which is sufficient for it to be classified as a 200m Sub-Twmpau. 

 

The full details for the hill are: 

Group:  Stiperstones 

Name:  Brimford Wood 

OS 1:50,000 map:  126

Summit Height:  258.3m (LIDAR) 

Summit Grid Reference:  SJ 30478 14400 (LIDAR) 

Bwlch Height:  236.2m (LIDAR) 

Bwlch Grid Reference:  SJ 30341 14320 (LIDAR) 

Drop:  22.1m (LIDAR) 

 

Myrddyn Phillips (October 2025)