Mapping Mountains – Summit Relocations – The Fours – The 400m Hills of England

 

Llanfair Hill (SO 255 785) 

There has been a Summit Relocation to a hill listed in 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 a Trimble GeoXH 6000 summit survey and LIDAR col analysis conducted by Myrddyn Phillips. 

LIDAR image of Llanfair Hill (SO 255 785)

The criteria for the list that this summit relocation 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 Llanfair Hill, and it is adjoined to the Cilfaesty group of hills, which are situated adoined to the Welsh border, and it is positioned encircled by minor roads, with the B4368 road farther to its north, the B4355 road farther to its south-west and the A488 road farther to its east, and has the town of Clun towards the east north-east.

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 twin 431m and c 431m summits with the 431m summit spot height positioned at SO 25592 78509 and an estimated c 431m twin summit height positioned at SO 25493 78438 that appear on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and an estimated c 417m col height, based on interpolation of 5m contouring between 415m – 420m.

The Trimble GeoXH 6000 gathering data at the summit of Llanfair Hill (SO 255 785)

However, it was not until the survey with the Trimble GeoXH 6000 and when 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. 

LIDAR summit image of Llanfair Hill (SO 255 785)

The Trimble GeoXH 6000 survey gives the summit of this hill as 430.6m positioned at SO 25594 78509 and LIDAR analysis confirms this is the highest ground on this hill and therefore its de-twinning, and this comes within the parameters of the Summit Relocations used within this page heading, these parameters are:

The term Summit Relocations applies when the high point of the hill is found to be positioned; in a different field, to a different feature such as in a conifer plantation,  within a different map contour either on Ordnance Survey maps or interactive mapping, to a different point where a number of potential summit positions are within close proximity, when natural ground or the natural and intact summit of a hill is confirmed compared to a higher point such as a raised field boundary or covered reservoir that is considered a relatively recent man-made construct, or the listing of a new twin summit or de-twinning of a summit, or a relocation of approximately 100 metres or more in distance from either the position of a map spot height or from where the summit of the hill was previously thought to exist.

Therefore, the summit height produced by the Trimble GeoXH 6000 survey is 430.6m and this is positioned at SO 25594 78509.  This position matches that of the spot height that appears on the Ordnance Survey 1:50,000 Landranger and 1:25,000 Explorer map and LIDAR analysis confirms the de-twinning of this summit.

 

The full details for the hill are:

Group:  Cilfaesty

Name:  Llanfair Hill

OS 1:50,000 map:  137, 148

Summit Height:  430.6m (Trimble GeoXH 6000)

Summit Grid Reference (New Position):  SO 25594 78509 (Trimble GeoXH 6000)

Col Height:  415.3m (LIDAR)

Col Grid Reference:  SO 25209 78802 (LIDAR)

Drop:  15.3m (Trimble GeoXH 6000 summit and LIDAR col)

 

Myrddyn Phillips and Aled Williams (March 2026)