Mapping Mountains – Significant Name Changes – The Welsh P15s

Cae Cefn Issa (SH 692 009) 

There has been a Significant Name Change to a hill that is listed in The Welsh P15s, 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 Cae Cefn Issa (SH 692 009)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s 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 the A493 road to its south, and has the town of Machynlleth towards the east.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in either the main list or the accompanying sub list, and was subsequently documented under the point (Pt. c 120m) notation with an estimated c 13m of drop, based on an estimated c 120m summit height and an estimated c 107m 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 179 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 Cae Cefn Issa in 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 The Welsh P15s is Cae Cefn Issa, and this was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Tarren y Gesail 

Name:  Cae Cefn Issa 

Previously Listed Name:  Pt. c 120m 

OS 1:50,000 map:  135

Summit Height:  119.5m (LIDAR)                                                           

Summit Grid Reference:  SH 69202 00955 (LIDAR)                                                  

Bwlch Height:  103.9m (LIDAR) 

Bwlch Grid Reference:  SH 69081 01055 (LIDAR) 

Drop:  15.5m (LIDAR) 

 

Myrddyn Phillips (December 2025) 

Mapping Mountains – Hill Reclassifications – The Welsh P15s

 

Cae Cefn Issa (SN 692 009) – Welsh P15 addition 

There has been an addition to the list of The Welsh P15s, 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 Cae Cefn Issa (SH 692 009)

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

The Welsh P15s – Welsh hills with 15m minimum drop, irrespective of their height, with an accompanying sub list entitled the Welsh Sub-P15s, with the criteria for this sub category being all Welsh hills with 14m or more and below 15m of drop.  The list is authored by Myrddyn Phillips, with the Introduction to the list appearing on Mapping Mountains on the 10^th May 2019. 

The Welsh P15s by Myrddyn Phillips

The name the hill is listed by is Cae Cefn Issa, and this was derived from the Tithe map, and it 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 the A493 road to its south, and has the town of Machynlleth towards the east.

When the listing that became known as The Welsh P15s was being compiled, this hill was not included in either the main list or the accompanying sub list, and was subsequently documented with an estimated c 13m of drop, based on an estimated c 120m summit height and an estimated c 107m 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

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 Welsh P15 status is due to LIDAR analysis, resulting in a 119.5m summit height and a 103.9m bwlch height, with these values giving this hill 15.5m 0f drop, which is sufficient for it to be classified as a Welsh P15. 

 

The full details for the hill are: 

Group:  Tarren y Gesail 

Name:  Cae Cefn Issa 

OS 1:50,000 map:  135

Summit Height:  119.5m (LIDAR)                                                           

Summit Grid Reference:  SH 69202 00955 (LIDAR)                                                  

Bwlch Height:  103.9m (LIDAR) 

Bwlch Grid Reference:  SH 69081 01055 (LIDAR) 

Drop:  15.5m (LIDAR) 

 

Myrddyn Phillips (December 2025)