Mapping Mountains – Significant Name Changes – Y Pedwarau – The 400m Hills of Wales

 

Pt. 464.7m (SO 041 681) 

There has been a Significant Name Change with the details being retrospective to a hill that is listed in the Y Pedwarau – The 400m Hills of Wales, with the summit height, bwlch height and their locations, the drop and status of the hill derived from LIDAR analysis initially conducted by Aled Williams and subsequently by Myrddyn Phillips. 

LIDAR image of Pt. 464.7m (SO 041 681)

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

Y Pedwarau – The 400m Hills of Wales.  Welsh hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list are five categories of sub hills; 500m Sub-Pedwarau, 500m Double Sub-Pedwarau, 400m Sub-Pedwarau, 390m Sub-Pedwarau and the 390m Double Sub-Pedwarau.  The list is co-authored by Myrddyn Phillips and Aled Williams and is published on Mapping Mountains in Google Doc format.

Y Pedwarau - The 400m Hills of Wales by Myrddyn Phillips and Aled Williams

The hill is adjoined to the Hirddywel group of hills, which are situated in the northern part of South Wales (Region B, Sub-Region B2), and it is positioned with minor roads to its west and south-east, and the A44 road to its south-west, and has the town of Rhaeadr Gwy (Rhayader) towards the west.

The hill appeared in the original Welsh 400m P30 list compiled by Myrddyn Phillips and published on Geoff Crowder’s v-g.me website, under the invented and transposed name of Pen yr Onnen, with an accompanying note stating; Name from buildings to the North-West.

Pen yr Onnen

465m

SO042682

136/147

200

Name from buildings to the North-West

When Myrddyn Phillips first compiled this list he thought it appropriate to either invent a name for a hill, or use a name that appeared near to the summit of the hill on Ordnance Survey maps of the day.  His preference was to use farm names and put Pen, Bryn or Moel in front of them.  This is not a practice that he now advocates as with time and inclination place-name data can be improved either by asking local people or by examining historic documents, through this form of research an appropriate name for the hill can usually be found. 

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

However, on occasion even when research is conducted an appropriate name for the hill may not be found, and on such occasions the listing protocol is to use the point notation, and this is the protocol adopted when Myrddyn Phillips and Aled Williams became co-authors of this list and the 1^st edition of the Y Pedwarau was published by Europeaklist in May 2013.  This hill was then listed under the point (Pt. 465m) notation with an estimated c 38m of drop, based on the 465m summit spot height that appears on the Ordnance Survey 1:25,000 Explorer map and an estimated c 427m bwlch height, based on interpolation of 10m contouring between 420m – 430m.

Therefore, the name this hill is now listed by in the Y Pedwarau – The 400m Hills of Wales is Pt. 464.7m, and this is being used as the authors have not found an appropriate name for the hill either through historic research and/or local enquiry. 

 

The full details for the hill are: 

Group:  Hirddywel 

Name:  Pt. 464.7m 

Previously Listed Name:  Pen yr Onnen 

OS 1:50,000 map:  136, 147 

Summit Height:  464.7m (LIDAR) 

Summit Grid Reference:  SO 04162 68135 (LIDAR) 

Bwlch Height:  428.9m (LIDAR) 

Bwlch Grid Reference:  SO 04102 68713 (LIDAR) 

Drop:  35.8m (LIDAR) 

 

Myrddyn Phillips and Aled Williams (April 2025)