Mapping Mountains – Significant Name Changes – 200m Twmpau

Garth Eryr (SH 785 556) 

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 Garth Eryr (SH 785 556)

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 Moel Siabod group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A5 road to its north and the A470 road to its south, and has the village of Betws-y-coed 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 under the point (Pt. 257m) notation with an estimated c 21m of drop, based on the 257m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 236m bwlch height, based on interpolation of 10m contouring between 230m – 240m. 

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

As the summit of this hill comprises bounded land the details for it were examined on the Tithe map.  The term Tithe map is generally given to a map of a Welsh or English parish or township and which was prepared after the 1836 Tithe Commutation Act.  This act allowed tithes to be paid in cash rather than goods.  The Tithe maps gave names of owners and occupiers of land in each parish and importantly for place-name research they also included the name of enclosed land.  This enclosed land is usually based on a field system, however not every field is given a name, but many are and especially so in Wales. 

Extract from the Tithe map

The enclosed land where the summit of this hill is situated is given the number 30 on the Tithe map, this can be cross referenced against the apportionments; it is these apportionments that give the name of the owner or occupier of the land as well as the name of the land.  The land where the summit of this hill is situated is named Garth Eryr in the apportionments, with the details on the Tithe map appearing in the parish named as Betws-y-coed and in the county named as Caernarfonshire. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the 200m Twmpau is Garth Eryr, and this was derived from the Tithe map. 

 

The full details for the hill are:

Group:  Moel Siabod

Name:  Garth Eryr

Previously Listed Name:  Pt. 257m   

OS 1:50,000 map:  115

Summit Height:  258.1m (LIDAR) 

Summit Grid Reference:  SH 78564 55666 (LIDAR) 

Bwlch Height:  232.4m (LIDAR) 

Bwlch Grid Reference:  SH 78533 55314 (LIDAR) 

Drop:  25.7m (LIDAR) 

 

Myrddyn Phillips (September 2025)