Mapping Mountains – Significant Name Changes – The Welsh P15s

 

Tai Isa (SH 780 620) 

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 Tai Isa (SH 780 620)

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 Carnedd Llywelyn group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A1), and it is positioned with minor roads to its north-west and south, with the B5106 road to its east, and has the town of Llanrwst towards the east.

When the listing that became known as The Welsh P15s was being compiled, this hill was listed under the point (Pt. 192m) notation, with an estimated c 15m of drop, based on the 192m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 177m bwlch height, based on interpolation of 10m contouring between 170m – 180m. 

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 70 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 Tai Isa in the apportionments, with the details on the Tithe map appearing in the parish named as Llanrhychwyn and in the county named as Caernarfonshire. 

Extract from the apportionments

Therefore, the name this hill is now listed by in the The Welsh P15s is Tai Isa, and this was derived from the Tithe map. 

 

The full details for the hill are: 

Group:  Carnedd Llywelyn 

Name:  Tai Isa 

Previously Listed Name:  Pt. 192m 

OS 1:50,000 map:  115

Summit Height:  193.2m (LIDAR)                                                           

Summit Grid Reference:  SH 78082 62044 (LIDAR)                                                  

Bwlch Height:  175.65m (LIDAR) 

Bwlch Grid Reference:  SH 77922 62033 (LIDAR) 

Drop:  17.6m (LIDAR) 

 

Myrddyn Phillips (May 2026)