The view from England of the main ridge separating it from Wales. Photo: Myrddyn Phillips

A Welshman who is a keen hillwalker and amateur surveyor believes research demonstrates his home nation should shrink a little and England could be expanded.

Myrddyn Phillips, with help from fellow walker Mark Trengove, spent months researching and surveying a hill that forms the boundary between the two nations.

The popular hill in south Wales has finally had the position of its summit confirmed, along with its relation to the land border between Wales and England, with possible consequences for the boundary between the two nations.

Here, the pair advance their case for a review of the Wales-England border on the south-eastern boundary of the Brecon Beacons, and detail the months of research that led them to their conclusion.

The hill rises above the Vale of Ewyas on its Welsh side, and the upper Olchon Valley on its English side. Even its name is under debate; is it the Welsh Twyn Llech or the English Black Mountain?

The Name

The hill is known by many as Black Mountain. However, research into the use of this name suggests that it was supplanted by early hill-list compilers from the old ridge name given to the main easterly spur of this hill range, and does not apply to the hill itself. This easterly ridge is now known as the Hatterrall Ridge after its southerly outlier, Hatterrall Hill.

Extensive local enquiries by Myrddyn Phillips with the local farming community unearthed the feature name of the Thieves’ Stone. This name was given by David Gains who farms in the Olchon Valley which is situated on the English side of the hill. Mr Gains said: “It’s hanging out on a slope, straight on top of the ridge, just on the Welsh side and about 3-4ft wide.”

He was asked when and how he had first heard of this name. He replied that his father had told him, saying that he’d heard: “If a sheep grazed the land around the stone and kept by the Thieves’ Stone it would never get maggots.”

This feature name still appears on contemporary Ordnance Survey maps in its Welsh form of Llech y Lladron, and is given to a rock outcrop on the upper and northerly section of this hill.

This and the name of Twyn Llech are the two main named features on this hill, and it is the latter that many know as this hill’s referred-to Welsh name, which can be translated as ‘hill of the stone or crag’. This name still appears on Ordnance Survey maps positioned to the west of its summit. Therefore for the remainder of this article we’ll refer to the hill as Twyn Llech.

Twyn Llech, which forms part of the border between Wales and England. Photo: Myrddyn Phillips

The Hill

Twyn Llech is positioned in the Black Mountains range of hills, situated in the south-eastern part of Wales. This hill range has four main extended ridges oriented in a north-west to south-east direction, and Twyn Llech is the highest point of the most easterly of these main ridges.

The hill comprises grass and heather with a base of peat. It is not dramatic in nature but is a great bulk of a hill. The high point is situated toward the northerly section of the main easterly ridge, which extends for approximately 15km (over nine miles). It has two main recognised and individual summits on it, one of which is Twyn Llech and the second the southerly outlier Hatterrall Hill.

There are two significant marker lines on contemporary Ordnance Survey maps that follow the course of this easterly ridge. One is a public right of way that designates a part of the Offa’s Dyke long-distance footpath, and the other is the land border between Wales and England. Both the public footpath and the land border are positioned next to one another on contemporary Ordnance Survey maps. As the summit of the hill is positioned to the west of the ridge path, it has generally been accepted that it is therefore in Wales, and over recent years the ridge path has been flagged in many sections to reduce encroaching erosion.

Introduction

Mark and I are both keen hillwalkers with a common interest in hill-bagging and the classification of hills. This particular hill was of interest, as its summit position and the location of the border between England and Wales, in relation to the summit, has been under debate. Was the summit of the hill on the Welsh side of the border and therefore could the hill be claimed as being Welsh, or was it on the English side and could the hill be claimed as being English? Our aim was to determine where the summit of the hill is positioned, measure its height and plot the course of the border between Wales and England as it crosses the summit plateau of Twyn Llech.

Research

Before visiting the hill I conducted extensive research in to the position of the border between Wales and England. My hope was to find a written document that gives detail of the position of this land boundary, and especially for the course that it takes over the main easterly ridge of the Black Mountains.

A number of individuals, public bodies and organisations were contacted including the Powys Archives, Powys County Council, National Library of Wales, Longtown Historical Society, Ewyas Study Group, Hereford Record Office, Brecon History Society, Clwyd Powys Archaeological Trust, Hereford Border Authorities, Electoral Services, Boundary Commission, Ordnance Survey, HMSO, Electoral Commission, local historians and the Senedd.

None of these individuals and organisations could either supply or give information on any form of written document to where the land border between Wales and England is positioned. In fact many said that such a document did not exist. The only organisation that gave any indication as to where this border is positioned was the Ordnance Survey, and they instructed me to consult their maps, as these would show the position of the border.

The summit

A distant Mark Trengove stands on the northern summit. Photo: Myrddyn Phillips

The summit area of this hill comprises a broad ridge of grass and heather with a base of peat. It is relatively flat in nature. However, Twyn Llech has a distinguishable rise on the northerly part of this land, and a dip that leads south to another slight rise approximately 350m away, with the northerly high point being relatively easy to distinguish and the southerly high point comprising land that slightly undulates.

These two rises, one to the north and one to the south, roughly match map detail. The Ordnance Survey give a 703m spot height on their contemporary 1:50,000 Landranger and 1:25,000 Explorer maps, positioned in the southerly part of a 700m continuous contour ring at grid reference SO 25586 35010. Harvey maps give a 706m spot height on their 1:40,000 Offa’s Dyke South map which is positioned in the northerly part of a 705m continuous contour ring.

First on-site visit

The first on-site visit concentrated on determining the height and position of the northerly high point and its counterpart to the south. This was conducted during an extended walk I completed, taking in a number of other hills. This also prioritised another hill to the south that was surveyed as having less that 15m of drop and which is currently still listed as a Nuttall. The conditions for each survey were excellent with good visibility and little breeze.

The results of these two surveys are:

• Northerly high point: 703.639m (converted to OSGM15) at SO 25520 35383
• Southerly high point: 702.721m (converted to OSGM15) at SO 25572 35032

A Trimble GeoXH 6000 GNSS receiver was used to determine the height of Twyn Llech and with a 0.9m difference in height there was confidence that the northerly point is where the summit of Twyn Llech is positioned. As the southerly land undulates a second survey to give correlation and confirmation was sought, and the opportunity to do so came nine months later.

The border

The second on-site visit gave Mark and me the opportunity to plot the course of the land border on the ground as it passes over the summit plateau of Twyn Llech. To do this we used a Garmin GPS Map 64s hand-held device that has access to the Ordnance Survey 1:50,000 mapping. By following the course of the border we determined that it was consistently positioned to the east of the flagged ridge path, and the path itself is also positioned to the east of the summit of both the northerly and southerly points. Having determined where the border lay according to 1:50,000 map detail, we paced from its position to where the Trimble was set-up on the northerly summit and its southerly counterpart, with the former being 50m and the latter being 45m in distance. Therefore, according to contemporary Ordnance Survey 1:50,000 mapping, the summit of Twyn Llech is in Wales.

However sometimes things aren’t as simple as they appear.

The flagged and maintained path leading to the northern high-point. Photo: Myrddyn Phillips

Second on-site visit

The second on-site visit had two aims. Firstly we wanted to determine the position of the land border according to Ordnance Survey 1:50,000 mapping, and secondly to take further data sets with the Trimble GeoXH 6000 from the northerly and southerly positions. The conditions for each survey were again ideal with good visibility and not a breath of breeze. The Trimble was placed on a rucksack, which was used as an improvised tripod to give elevation above its immediate surrounds. Respective measurement offsets were taken between its internal antenna and the ground below.

The results of these three further surveys are:

• Northerly high point: 703.656m (converted to OSGM15) at SO 25520 35383
• Southerly high point: 702.787m (converted to OSGM15) at SO 25558 35018
• Southerly high point: 702.699m (converted to OSGM15) at SO 25566 35054

These results show excellent correlation with the first set of survey data and confirm that the northerly point is where the summit of Twyn Llech is positioned.

Map comparison

Our on-site visit had confirmed where the summit of Twyn Llech is positioned and had given the hill an accurate height. It also seemed to confirm that the border between Wales and England is approximately 50m to the East of the summit and therefore the high point of the hill is in Wales. However, to confirm the position of the border we wanted to compare the other publicly available scale of Ordnance Survey map: the 1:25,000 Explorer series and then compare these details against the series of Ordnance Survey six-inch maps.

As the 1:25,000 Explorer map gave the position of the border as no more than 10-15m from the summit of the hill, compared to the 50m of the 1:50,000 Landranger map we now turned to the series of six-inch maps.

The Ordnance Survey base map

A detail from the six-inch map, with the word 'watershed' marked against the border

For many years the Ordnance Survey six-inch map was considered their base map. This was the map for information to be fed on to. The scale was superseded in the 1950s by the 1:10,000 series of maps and was available as sheets until the 1980s when these maps were digitised. The six-inch map is still one of the best for giving detail, either numerical or positional.

We consulted the series of six-inch maps and looked at detail surveyed in 1887 and published in the same year. The land border between Wales and England appears on this map as a split black line, as it does on the publicly available scales of 1:50,000 and 1:25,000 maps. However, the line of this border on the six-inch map has one extremely important word placed against it: watershed.

The word watershed also appears beside this border on the Ordnance Survey Vector Map Local that is hosted on the Geograph website and entitled the Interactive Coverage Map. Therefore this word and its implication have remained in the system of Ordnance Survey mapping for more than 130 years.

Ordnance Survey consultation

As there was discrepancy between our on-site findings using the 1:50,000 mapping and the six-inch and Vector Map Local maps the Ordnance Survey were consulted and they kindly forwarded the following information.

“Ordnance Survey are not directed by the Ordnance Survey Act 1841 or any other Act to show national boundaries, although they are shown on certain scales of mapping (1:50k/Landranger, does depict national boundaries between England-Wales, England-Scotland). In OS’s most detailed mapping product OS MasterMap the Welsh-English border is located accurately and correctly. It is displayed as a County/UA boundary.

“OS’s 1:25k and 1:50k leisure maps are purely contextual to provide a navigational guide to the landscape. Given their scale, these maps should never be used for measuring and surveying purposes. Our leisure maps are derived from the accurate large-scale data but are generalised for clarity, therefore not every feature is shown in the same position as the source data, and we are satisfied with how they currently depict the location of the Welsh-English border.”

The OS MasterMap is the Ordnance Survey digitised mapping which receives upwards of 10,000 individual updates per day and as its name implies, this is the master map for Ordnance Survey data.

I was advised by Ordnance Survey that the placement of the border on MasterMap is 12m to the East of the grid coordinates I supplied them for the summit position of Twyn Llech, and this means that MasterMap places the summit of this hill in Wales.

Boundary Commission for Wales consultation

The equipment in operation during the third survey of the southern point. Photo: Myrddyn Phillips

After consultation with Ordnance Survey I was advised to contact the Boundary Commission for Wales. It is this organisation that if a change in border placement is required would instigate it. This organisation kindly forwarded the following:

“There is no legal mechanism for reviewing the boundary between England and Wales. The boundary is fixed and would require primary legislation to develop a mechanism to make a change to it. The England-Scotland boundary does have such a mechanism and the review is performed jointly by the English and Scottish Boundary Commissions.

“As far as the commission is concerned the boundary provided by Ordnance Survey, particularly that in its MasterMap product, is the definitive boundary.

“With regard to the specific area to which you referred, I confirm that it is the convention of this commission that if we were to draw a boundary that it would follow either the top of a ridge-line to its peak or the bottom of a valley depending on the circumstance, where we are not following another easily identifiable boundary (road, railway line, centre of a river, etc). It may be that when the boundary was originally drawn at the larger scale that that was the intention. We have no records which would ascertain that intention.”

Conclusion

My conclusion from the research and survey I have conducted with the assistance of Mark Trengove is that the border should be moved and placed on MasterMap going through the summit of Twyn Llech and that primary legislation should be initiated to instigate the mechanism required for such a change.

Myrddyn Phillips

This is based on the convention the Boundary Commission for Wales would adopt and the evidence that the border followed the watershed on this hill’s summit plateau on selective Ordnance Survey maps for more than 130 years.

It is also based on the fact that it is the natural course of any boundary on an open mountain such as Twyn Llech to follow the ridge crest which is also the watershed. The simple fact of the matter is that no one had ever surveyed this hill for where its summit is positioned prior to our visit. Therefore, the border placement on MasterMap although very close to the summit is still 12m from it and in all probability the cartographer who placed it was doing so to where they thought the watershed lay.

Myrddyn Phillips with Mark Trengove