Mapping Mountains – Significant Name Changes – 100m Twmpau

Crwn Hir (SN 670 993) 

There has been a Significant Name Change to a hill that is listed in the 100m 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 Crwn Hir (SN 670 993)

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

100m Twmpau - Welsh hills at or above 100m and below 200m in height that have 30m minimum drop, with an accompanying sub list entitled the 100m Sub-Twmpau, with the criteria for this sub category being all Welsh hills at or above 100m and below 200m 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. 

100m Twmpau by Myrddyn Phillips

The hill is adjoined to the Tarren y Gesail group of hills, which are situated in the south-western part of North Wales (Region A, Sub-Region A3), and it is positioned with a minor road to its north and the A493 road to its east, and has the village of Cwrt towards the east north-east.

When the original 100m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the 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-assessed and it was listed under the point (Pt. c 146m) notation with an estimated c 20m of drop, based on an estimated c 146m summit height and an estimated c 126m bwlch height, with both heights based on interpolation of 10m contouring that appears on the Ordnance Survey 1:25,000 Explorer map. 

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 342 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 Crwn Hir the apportionments, with the details on the Tithe map appearing in the parish named as Tywyn and in the county named as Merioneth. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the 100m Twmpau is Crwn Hir, and this was derived from the Tithe map. 

 

The full details for the hill are:

Group:  Tarren y Gesail

Name:  Crwn Hir

Previously Listed Name:  Pt. c 146m   

OS 1:50,000 map:  135

Summit Height:  151.4m (LIDAR) 

Summit Grid Reference:  SN 67079 99365 (LIDAR) 

Bwlch Height:  121.25m (LIDAR) 

Bwlch Grid Reference:  SN 67030 99444 & SN 67034 99447 (LIDAR) 

Drop:  30.1m (LIDAR) 

 

Myrddyn Phillips (October 2025)