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)

Monthly Synopsis

 

Synopsis of all major changes detailed on Mapping Mountains during the last calendar month.  These can include new, confirmation and retrospective changes

 

Hill Reclassifications: 

Crug Siarls (SN 702 483) - 390m Sub-Pedwar deletion

Bryn Caniadau (SH 764 617) - Welsh Sub-P15 deletion

Llanfair Hill (SO 255 785) - Sub-Four addition

Troed Rhiw Bylchau (SN 761 471) - Sub-Trichant addition

 

Significant Height Revisions: 

Yr Eifl (SH 364 447) - 500m Twmpau, Y Trechol - The Dominant Hills of Wales and Welsh Highlands - Uchafion Cymru

Ysgafell Wen (SH 663 487) - Welsh Highlands - Uchafion Cymru and Y Pellennig - The Remotest Hills of Wales

Bryn Caniadau (SH 764 617) - The Welsh P15s

Summit Relocations: 

Graig Wen (SN 786 629) - Y Pellennig - The Remotest Hills of Wales

Significant Name Changes: 

Burton Howe (NZ 607 032) - The Fours  The 400m Hills of England

Mapping Mountains – Hill Reclassifications – Y Trichant – The 300m Hills of Wales

 

Troed Rhiw Bylchau (SN 761 471) – Sub-Trichant addition

There has been an addition to the list of Y Trichant – The 300m Hills of Wales, 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 Troed Rhiw Bylchau (SN 761 471)

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

Y Trichant – The 300m Hills of Wales – Welsh hills at or above 300m and below 400m in height that have 30m minimum drop, with an accompanying sub list entitled the Sub-Trichant, with the criteria for this sub category being all Welsh hills at or above 300m and below 400m in height with 20m or more and below 30m of drop.  The list is authored by Myrddyn Phillips with the Introduction to the list and the renaming of it appearing on Mapping Mountains on the 13^th May 2017, and the Introduction to the Mapping Mountains publication of the list appearing on the 1^st January 2022. 

Y Trichant - The 300m Hills of Wales by Myrddyn Phillips

The name the hill is listed by is Troed Rhiw Bylchau, and it is adjoined to the Esgair Wen group of hills, which are situated in the central part of South Wales (Region B, Sub-Region B1), and it is positioned with minor roads to its north-east and south-west, and has the town of Llanwrtyd towards the east.

When the original 300m height band of Welsh P30 hills were published on Geoff Crowder’s v-g.me website, this hill was not included in the accompanying Hills to be surveyed sub list, as it was considered not to meet the criteria then used for this sub category.

After the sub list was standardised, and interpolated heights and drop values also included the details for this hill were re-evaluated and it was listed with 19m of drop, based on the 383m summit spot height that appears n the Ordnance Survey 1:25,000 Explorer map and the 364m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage 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 Sub-Trichant status is due to LIDAR analysis, resulting in a 387.8m summit height and a 360.6m bwlch height, with these values giving this hill 27.1m of drop, which is sufficient for it to be classified as a Sub-Trichant.

 

The full details for the hill are: 

Group:  Esgair Wen 

Name:  Troed Rhiw Bylchau 

OS 1:50,000 map:  146, 147

Summit Height:  387.8m (LIDAR)                                                           

Summit Grid Reference:  SN 76197 47177 (LIDAR) 

Bwlch Height:  360.6m (LIDAR) 

Bwlch Grid Reference:  SN 76205 47017 & SN 76217 47008 (LIDAR) 

Drop:  27.1m (LIDAR) 

 

Myrddyn Phillips (February 2026)

Mapping Mountains – Significant Height Revisions – The Welsh P15s

Bryn Caniadau (SH 764 617) 

There has been a Significant Height Revision to a hill that was 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 Bryn Caniadau (SH 764 617)

The criteria for the list that this height revision 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 Bryn Caniadau, and this was derived from the Ordnance Survey series of Six-Inch maps, and it 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 east, with the A5 road to its south and the B5106 road and the A470 road towards its east, and has the town of Llanrwst towards the east. 

Extract from the Ordnance Survey series of Six-Inch maps

When the listing that became known as The Welsh P15s was being compiled, this hill was included in the P14 sub list with an estimated c 14m of drop, based on an estimated c 213m summit height and an estimated c 199m 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. 

LIDAR summit image of Bryn Caniadau (SH 764 617)

The summit height produced by LIDAR analysis is 215.1m and when compared to the previously listed summit height, this comes within the parameters of the Significant Height Revisions used within this page heading, and these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey, Harvey or other interactive map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000 or analysis of data produced via LIDAR.  Also included are hills whose summit map data is missing an uppermost ring contour when compared with the data produced by the Trimble or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 215.1m and this was derived from LIDAR analysis.  This is 2.1m higher than the previous listed summit height of c 213m, which was based on interpolation of the uppermost 210m ring contour that appears on the Ordnance Survey 1:25,000 Explorer map.

 

The full details for the hill are: 

Group:  Carnedd Llywelyn 

Name:  Bryn Caniadau 

OS 1:50,000 map:  115

Summit Height (New Height):  215.1m (LIDAR)                                                           

Summit Grid Reference:  SH 76492 61758 (LIDAR)                                                  

Bwlch Height:  201.2m (LIDAR) 

Bwlch Grid Reference:  SH 76439 61684 (LIDAR) 

Drop:  13.9m (LIDAR) 

 

Myrddyn Phillips (February 2026)

  

Mapping Mountains – Significant Height Revisions – Y Pellennig – The Remotest Hills of Wales and Welsh Highlands – Uchafion Cymru

 

Ysgafell Wen (SH 663 487) 

There has been a Significant Height Revision that is retrospective to a hill that is listed in the Y Pellennig – The Remotest Hills of Wales and the Welsh Highlands – Uchafion Cymru, with the summit height, bwlch height and their locations, the drop and status of the hill derived from a Leica RX1250 survey conducted by Alan Dawson. 

LIDAR image of Ysgafell Wen (SH 663 487)

The criteria for the two listings that this height revision applies to are:

Y Pellennig –The Remotest Hills of Wales - Welsh hills whose summit is at least 2.5km from the nearest paved public road and the hill has a minimum 15m of drop.  The list is co-authored by Myrddyn Phillips and Aled Williams and is available as a downloadable e-booklet or print-booklet version on Mapping Mountains Publications with the up-to-date master list available on Mapping Mountains to download in Google Doc format. 

Y Pellennig - The Remotest Hills of Wales by Myrddyn Phillips and Aled Williams

Welsh Highlands – Uchafion Cymru – Welsh hills at or above 500m in height with 15m minimum drop, with an accompanying sub list entitled the Welsh Highland Subs, the criteria for which is all Welsh hills at or above 500m in height with 10m or more and below 15m of drop.  This list is authored by Myrddyn Phillips and Aled Williams with the Introduction to the list published on Mapping Mountains in November 2015 and the latest update relating to the list published on Mapping Mountains in January 2023.

Welsh Highlands - Uchafion Cymru by Aled Williams and Myrddyn Phillips

The name the hill is listed by is Ysgafell Wen and it is adjoined to the Moelwyn Mawr group of hills, which are situated in the north-western part of North Wales (Region A, Sub-Region A2), and it is positioned with the A498 road to its north-west, a minor road to its west and the A470 road to its east, and has the town of Blaenau Ffestiniog towards the south-east. 

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

When the original list that later became known as the Welsh Highlands – Uchafion Cymru was first compiled, this hill was listed with an estimated c 16m of drop, based on a basic levelling survey conducted by John and Anne Nuttall, with the summit height ascertained by the addition of the drop value to the 641m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map. 

LIDAR summit image of Ysgafell Wen (SH 663 487)

However, it was not until a survey with GNSS equipment that an accurate summit height for this hill could be ascertained.  This was conducted by Alan Dawson on the 12.06.17 using a Leica RX1250, resulting in a 659.0m summit height positioned at SH 66384 48768, and this comes within the parameters of the Significant Height Revisions used within this page heading, these parameters are:

The term Significant Height Revisions applies to any listed hill whose interpolated height and Ordnance Survey or Harvey map summit spot height has a 2m or more discrepancy when compared to the survey result produced by the Trimble GeoXH 6000, the Leica RX1250 or analysis of data produced via LIDAR, also included are hills whose summit map data is missing an uppermost ring contour when compared to the data produced by the Trimble, Leica RX1250 or by LIDAR analysis.

Therefore, the new listed summit height of this hill is 659.0m and this was derived from a Leica RX1250 survey, this is 2.0m higher than the previously listed height of c 657m, which was based on a 16m basic levelling survey conducted by John and Anne Nuttall, with the summit height ascertained by the addition of the drop value to the 641m bwlch spot height that appeared on the Ordnance Survey Vector Map Local hosted on the Geograph website and which was entitled the Interactive Coverage Map.

 

ills of Wales, and are reproduced below@

The full details for the hill are:

Group:  Moelwyn Mawr

Name:  Ysgafell Wen

OS 1:50,000 map:  115

Summit Height (New Height):  659.0m (converted to OSGM15, Leica RX1250) 

Summit Grid Reference:  SH 66384 48768 (Leica RX1250) 

Bwlch Height:  639.9m (converted to OSGM15, Leica RX1250) 

Bwlch Grid Reference:  SH 66380 48665 (Leica RX1250) 

Drop:  19.1m (Leica RX1250) 

Remoteness:  2.760km

 

Myrddyn Phillips and Aled Williams (February 2026)

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

 

Llanfair Hill (SO 255 785) – 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 a Trimble GeoXH 6000 summit survey and LIDAR col analysis conducted by Myrddyn Phillips. 

The ancient embankment of Offa's Dyke beside the summit of Llanfair Hill (SO 255 785)

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 Llanfair Hill, and it is adjoined to the Cilfaesty group of hills, which are situated adjoined 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 image of Llanfair Hill (SO 255 785)

Therefore, the addition of this hill to Sub-Four status is due to a Trimble GeoXH 6000 summit survey and LIDAR col analysis, resulting in a 430.6m summit height and a 415.3m col height, with these values giving this hill 15.3m of drop, which is sufficient for it to be classified as a Sub-Four. 

 

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:  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)

 

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 (February 2026)