Mapping Mountains – Hill Reclassifications – The Fours – The 400m Hills of England

 

Rhos Ffidl (SO 206 854) – Sub-Four addition

There has been an addition to the listing of the The Fours – The 400m Hills of England, with the summit height, col height and their locations, the drop and status of the hill derived from LIDAR analysis conducted by Myrddyn Phillips. 

LIDAR image of Rhos Ffidl (SO 206 854)

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

The Fours – The 400m Hills of England - English hills at or above 400m and below 500m in height that have 30m minimum drop, accompanying the main list is a sub list entitled the Sub-Fours, the criteria for which are all English hills at or above 400m and below 500m in height that have 15m or more and below 30m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available to download in Google Doc format from the Mapping Mountains site.

The Fours - The 400m Hills of England by Myrddyn Phillips and Aled Williams

The name the hill is listed by is Rhos Ffidl, and it is adjoined to the Cilfaesty group of hills, which are situated adjoined to the Welsh border, and it is positioned with minor roads to its north-east and north-west, and the B4368 road towards the south, and has the village of Ceri (Kerry) towards the north-west.

When the Introduction to the first group of hills for the updated and revised listing of the The Fours – The 400m Hills of England was published by Mapping Mountains on the 10^th September 2022, it was announced that the accompanying sub lists were being revised with the two 390m categories dispensed with and the criteria and name of the 400m Sub-Fours revised.  The one accompanying sub list is now named the Sub-Fours with its criteria being all English hills 400m and above and below 500m in height that have 15m and more and below 30m of drop. 

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

Prior to this revision this hill was listed with an estimated c 14m of drop, based on the 422m summit spot height that appears on the Ordnance Survey 1:50,000 Landranger map and an estimated c 408m col height, based on interpolation of 5m contouring between 405m – 410m. 

Extract from the Ordnance Survey 1:50,000 Landranger 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 Sub-Four status is due to LIDAR analysis, resulting in a 422.7m summit height and a 407.1m col height, with these values giving this hill 15.7m of drop, which is sufficient for it to be classified as a Sub-Four. 

 

The full details for the hill are:

Group:  Cilfaesty

Name:  Rhos Ffidl

OS 1:50,000 map:  137

Summit Height:  422.7m (LIDAR)

Summit Grid Reference:  SO 20652 85426 (LIDAR)

Col Height:  407.1m (LIDAR)

Col Grid Reference:  SO 20510 85766 (LIDAR)

Drop:  15.7m (LIDAR)

 

For the additions, deletions and reclassifications to The Fours – The 400m Hills of England reported on Mapping Mountains since the December 2013 publication of the 1^st edition of this list by Europeaklist please consult the following Change Registers:

 

The Fours

 

Sub-Fours

 

Myrddyn Phillips and Aled Williams (May 2026)