A holiday in West Wales in the early Autumn of 2022 led to a little research on the railways in the area.
This is the sixth article about Pembrokeshire’s Railways. The first focussed on the pre-railway age, the second focussed on the mainline railways of the county. The third article focussed on the industrial railways in the vicinity of Milford Haven. The fourth and fifth on the Saundersfoot Railway in Pembrokeshire. The links to these posts are provided below. This article concentrates on the railways associated with RNAD Trecwn (the Royal Navy Armaments Depot at Trecwn).
The Royal Navy Armaments Depot at Trecwn (RNAD Trecwn)
RNAD Trecwn is, in the 21st century, a decommissioned Royal Navy Armaments Depot, south of Fishguard in the village of Trecwn, Pembrokeshire, West Wales.
It was built in 1938 to store and supply naval mines and munitions ordnance to the Royal Navy. The depot apparently came into its own during the cold war. During those times 400 permanent workers were employed at the site, housed in an MoD built small town. The site had an on-site, 2ft 6in (762mm) narrow gauge railway, built using copper to reduce sparks. Weapons were both delivered to the site and then distributed using standard gauge rail to Fishguard, Neyland for Milford Haven, and latterly Pembroke Dock. 
The Standard-gauge Branch Line and Sidings – Just south of the main entrance to RNAD Trecwm and the main security fence to the site was a single railway platform, for workers access to the depot. Within the security fence, a marshalling yard of 8 parallel loops existed, shunted by a dedicated MoD diesel hydraulic shunting locomotive. The line then extended on down the valley, through a gauge exchange shed for access to the narrow gauge network, and then provided direct access to the 58 cavern storage chambers via a series of herring-bone shaped sidings. 
Supply trains would run along the dedicated branch-line from the site: to Fishguard Harbour; to Neyland for Milford Haven; and Pembroke Dock. At Fishguard the line extended beyond the ferry terminal at Fishguard Harbour railway station, continuing along the breakwater to a single line spur, allowing for transfer of munitions to Royal Navy ships. 
These next few images show the Trecwn branch-line. The first shows its junction with what was the GWR line to Fishguard from which the branch runs Northeast towards Trecwn …
The depot was decommissioned in 1992. All 58 cavern storage bunkers and the extensive above ground network of storage sheds and other military buildings remain in place. Ownership of the site was transferred from the Ministry of Defence to Anglo-Irish consortium Omega Pacific in 1998, and then by court order to the Manhattan Loft Corporation in 2002. The site is being redeveloped as an industrial park. 
Three aerial photographs are provided by the Fishguard and Goodwick Local History Society. Posted by Ian Evans, they are used here by kind permission.
The first one shows the main entrance to the depot at it’s southern end. It can be dated to the mid-1950’s. “At the bottom right of the image can be seen the main railway line into the valley, leading to the railway sidings. The buildings to both sides of the railway sidings included a number of specialist workshops and storage facilities, there were no live explosives handled in this area.” 
The second “shows the workshops and stores buildings in more detail. The building at the bottom right with the tall chimneys was the southern boiler house which supplied steam to most of the buildings seen here. It was in this area that the narrow gauge railway system started, it extended right up the north end of the site.” 
Of interest, to me at least, is that when I load Google Earth onto my desktop I automatically get the railway tracks at Trecwn added. I am not sure how that happened, but it is useful for this article. ….
The third of three aerial images from the mid-1950s appears below. It “shows the red area where live explosives were handled and stored, everything from .303 Rifle bullets to 1 Thousand pound bombs were processed here and stored in 58 Magazines built into each side of the valley, If you zoom in you can see a number of the tunnel entrances quite clearly. A lot of the smaller buildings have blast walls surrounding them. The complex extended further north from this photo to the north end Boiler House and security gates.” 
The OpenRailwayMap  is also of great help in establishing what railways existed inside the Depot. It is clear that the standard-gauge line extended much further to the Northeast along the valley of the Afon Aer than the Ordnance Survey mapping records.
To complete this section on the Standard-gauge line, I have included a series of screen-dumps from the OpenRailwayMap . Having them at this point in the article should hopefully minimise scrolling when we look at the Narrow-Gauge network at the depot. The sequence of the map extracts runs from the Depot gates in the West, closest to the hamlet of Trecwn, eastwards to the point where the valley turns to the North and then follows the valley northwards.
This final image is the key/legend provided by the OpenRailwayMap  editors. The Trecwn branch as far as the depot gates is shown in yellow above. The standard-gauge lines within the Depot are deemed industrial lines and are therefore shown as thin brown lines. The length of these line inside the Depot is significantly longer that that shown on the Ordnance Survey maps. Abandoned standard gauge lines are shown as thick dashed brown lines (not grey as in the key).
The narrow gauge lines are shown as thin dashed brown lines. It is possible that by the time the mapping was undertaken these had been abandoned and are hence shown dashed. There are a very few lengths of narrow-gauge track shown solid brown.
The extent of the network of these lines is, for me, the most engaging element of this mapping. RNAD Trecwn had a very significant internal narrow-gauge network. …
The Narrow Gauge (2ft 6in) Lines – A 2ft 6in (762 mm) gauge network traverses the entire site, with direct access to the 58 cavern storage chambers. All rail infrastructure was built in copper to reduce the risk of sparks. Serviced via its own on-site locomotive shed and works, the line was equipped with a series of specially provided wooden enclosed wagons, with sliding roof covers. This allowed sea mines and other munitions to be directly placed within the wagons from overhead gantries, and transported over the entire site without access via any form of side door, hence enhancing safety. The narrow gauge line therefore became the main method of on-site distribution, with standard gauge rail or road the off site access method. 
The next few aerial images can be found on the Coflein website and show elements of the narrow-gauge system running along the site. In places the standard-gauge and narrow -gauge sit side-by-side.
In 2003, David Mansell, writing about the site commented: “About a mile into the site the narrow gauge railway facilities commence with maintenance sheds and a covered transfer building. There are a total of 58 storage chambers, each extending into the hillside for 200 feet, arranged in a herringbone formation along both sides of the valley. Each one has alarmed steel doors with its own siding off the narrow gauge railway.”  … His opinion at the time, was that RNAD Trecwn was “a railway enthusiasts dream with both standard and narrow (2ft 6in) gauge lines. The depot has its own branch off the Fishguard to Carmarthen line and after a small platform area outside the depot for staff the line enters the site via lockable steel gates into the main marshalling yard where the line splits into 8 parallel loops. The standard gauge line then travels the entire length of the valley alongside the narrow-gauge line which has points for the siding to each storage chamber.”  …
The narrow gauge rolling stock then consisted of the “well known ‘Trecwn’ wooden wagons with sliding roofs to enable mines to be lowered in and flatbed trucks for other munitions. Some of the stock can now be seen on the Welsh Highland and [Welshpool and] Llanfair light railways.” 
At the time Dave Mansell was writing, there was still a substantial amount on site. Locomotives included small diesel shunters and battery units; some derelict examples of which were still on the site in 2003. Points on both gauges were manually operated and still well greased. 
The next few photographs were all taken early in 2003 by Dave Mansell and are shared with his kind permission and that of Subterranea Britannica…..
Locomotives – a series of narrow-gauge locomotives were employed at the site. These are surviving examples:
Ruston & Hornsby 187069 – was a Class 25/30hp locomotive with a Ruston 3VSO engine and weighing 3.25 tons. It left the works on 28th October 1937. “It was one of forty of that type working on the Nuttall-Pauling Consortium contract to build the … Depot at Trecwn. … Construction was complete by 1941 but this locomotive was evidently still in the West of Wales in 1950, because a spares order was placed by Pauling on 26th May 1950 to be sent to Geo Bros Ltd., East Burrows Yard, Swansea, which may have been repairing it. In 1951 it was noted at Pauling’s Park Royal plant depot, Middlesex, numbered P250 in the Pauling list. It was later sold or scrapped at an unknown date. [229: p1-2]
Baguley-Drewry Locomotives – Baguley-Drewry of Burton-on-Trent built a number of locomotives for this narrow gauge network.
The Talyllyn railway purchased two of Trecwn’s narrow-gauge locomotives …. Diesel No.11 “Trecwn” & No.12 “St Cadfan” were purchased by Talyllyn volunteers from RNAD Trecwn in 2008. The names were decided by ballot in 2014 by the group that originally purchased the locomotives for the Talyllyn. Both Locomotives were re-gauged from 2ft 6in to the Talyllyn’s 2ft 3in Gauge. Talyllyn members also purchased over a mile of track from RNAD Trecwn complete with rail, sleepers, spikes and fishplates in June 2008. 
1. M.R. Connop-Price; Pembrokeshire: the Forgotten Coalfield; Landmark Publishing, Ashbourne, Derbyshire, 2004
32. D S M Barrie, revised Peter Baughan; A Regional History of the Railways of Great Britain: volume 12: South Wales; David St John Thomas, Nairn, 1994.
36. Wing Commander Ken McKay; A Vision of Greatness: The History of Milford 1790-1990; Brace Harvatt Associates, 1989.
56. https://en.m.wikipedia.org/wiki/RNAD_Trecwn, accessed on 13th September 2022.
57. https://maps.nls.uk/view/102188136, accessed on 13th September 2022.
58. https://commons.m.wikimedia.org/wiki/File:Statfold_Barn_Railway_-RNAD_Trecwn_A10(geograph_4220678).jpg, accessed on 13th September 2022.
59. https://alchetron.com/RNAD-Trecwn, accessed on 14th September 2022.
60. https://maps.nls.uk/view/91857083, accessed on 14th September 2022.
61. https://coflein.gov.uk/en/site/96059, accessed on 14th September 2022.
229. Martin Shill; Number 250; in the Industrial Railway Record, Industrial Railway Society Volume 250 September 2022, p1-6.
230. https://maps.nls.uk/geo/explore/#zoom=15.0&lat=51.95523&lon=-4.93724&layers=6&b=1, accessed on 29th September 2022.
231. https://maps.nls.uk/geo/explore/#zoom=16.0&lat=51.95468&lon=-4.95372&layers=6&b=1, accessed on 29th September 2022.
232. https://maps.nls.uk/view/102188136, accessed on 29th September 2022.
233. https://maps.nls.uk/view/102188163, accessed on 29th September 2022.
234. https://www.subbrit.org.uk/sites/trecwn-royal-naval-armaments-depot, accessed on 29th September 2022.
235. https://www.openrailwaymap.org, accessed on 29th September 2022.
236. OpenRailwayMap (previously called “Bahnkarte”) is a detailed online map of the world’s railway infrastructure, built on OpenStreetMap data. It has been available since mid-2013 at openrailwaymap.org. This project was founded in December 2011 in order to create a world-wide, open, up-to-date and detailed map of the railway network, based on OpenStreetMap. The domain was registered on April 27th, 2013 and the corresponding website was launched in mid 2013. Since then it has received constant improvement. In February 2014 the project moved to a new server. In April 2014 a dedicated map for mobile phones was launched. 
The OpenRailwayMap includes all rail-mounted and automotive vehicles, e.g. railways, subways, trams, miniature railways and funiculars. The map does not include aerialways, monorails, and maglevs. The name OpenRailwayMap mostly refers to the online map, but the project also aims to support railroad-related data in OpenStreetMap. By developing a consistent data model, providing a mailing list for discussions, developing editor plugins, etc. the collection of these data is boosted and the data are made usable for other applications and developers. 
237. https://wiki.openstreetmap.org/wiki/OpenRailwayMap, accessed on 29th September 2022.
238. https://commons.wikimedia.org/wiki/File:Old_branch_line_to_Trecwn_-geograph.org.uk-_520836.jpg, accessed on 29th September 2022.
239. https://commons.wikimedia.org/wiki/File:Level_crossing_on_dead_railway_-geograph.org.uk-_1855840.jpg, accessed on 29th September 2022.
240. https://commons.wikimedia.org/wiki/File:Branch_to_Trecwn_-geograph.org.uk-_208673.jpg, accessed on 29th September 2022.
241. This statement needs a minot clarification. The Trecwn Branch used to leave the line between Fishguard and Clynderwen just South of where that line diverged from the route from Fishguard tthrough Clarbeston Road. The North Pembrokeshire line was lost many years before the Trecwn branch closed. The tracks visible in the image above led only to Trecwn.
242. http://disused-stations.org.uk/features/north_pembrokeshire_and_fishguard_railway/index.shtml, accessed on 29th September 2022.
243. https://m.facebook.com/groups/trulypembrokeshire/permalink/755957217781489, accessed on 30th September 2022.
244. https://www.flickr.com/photos/rocketron7/albums/72157647842795154, accessed on 30th September 2022.
245. https://www.facebook.com/profile.php?id=100065502640813 … Ron Weatherall 17th. August 2017, accessed on 30th September 2022.
246. https://commons.m.wikimedia.org/wiki/File:Talyllyn_Railway_No_11_Trecwn_-_2018-06-16.jpg, accessed on 2nd October 2022.
247. https://www.hanesabergwaun.org.uk/places/industry-businesses/trecwn-aerial-views-rnad-trecwn, accessed on 2nd October 2022.
248. https://amertonrailway.co.uk/locomotives/diesel/a10, accessed on 10th October 2022.
249. https://amertonrailway.co.uk/events/everything-goes-gala, accessed on 10th October 2022.
250. http://www.rdwales.co.uk/trecwn-valley.htm, accessed on 2nd October 2022.
251. https://www.facebook.com/167680895449/posts/pfbid0wU9efHT2NErDUrXJpn7cf1nf9v8aXwQZBU7WR1qCEpwcpDTgM4bKhMNxJV8N8JD3l/?app=fbl, accessed on 10th October 2022.