South Duffryn or ‘Plymouth’ Colliery, situated to the south of Pentrebach and just north of Troedyrhiw, was opened by the Hills Plymouth Company in 1862. It was served by the Taff Valley Railway and the Penydarren Tramroad. I have been prompted to write this short post by reading an article written by Clive Thomas in the Archive Journal of September 2014. 
The featured image above shows the colliery sidings in a postcard image from the early 20th century.  The colliery itself is just off the picture to the right. Most of the wagons in the picture seem to be privately owned by the Plymouth Collieries. The sidings are all standard-gauge and were served by the Taff Valley Railway. A number of the buildings of the disused Duffryn Ironworks can be seen in the centre of the image. Some of these were later used as workshops for the colliery. 
Some basic information about the area us provided by Alan George in his website about Old Merthyr Tydfil.  … Clive Thomas tells the story of the Plymouth Ironworks and Collieries in Archive Journal No. 83:
“In 1786, a lease was secured from the Earl of Plymouth on a tract of land on the East bank of the River Taff and to the south of the hamlet of Merthyr Tydfil. From that date, the name of the ironworks established there became synonymous with that of the Hill family. For seventy years, first Richard and then each of his three sons, Richard (Jnr), John and Anthony played their part in its development as one of South Wales’ pre-eminent iron-making concerns.
The Plymouth Ironworks, which grew at the three sites of Plymouth, Pentrebach and Duffryn, although never seriously rivalling it’s neighbours at Cyfarthfa and Dowlais in terms of size and iron ore production, should not be regarded as an insignificant player in the history of iron manfacture. By the mid 1840s, the ironworks consisted of ten blast furnaces, twenty-four puddling furnaces, four forges and seven rolling mills, as well as the ancillary machinery and mines associated with iron production. The works had been advertised for sale in 1834, but no buyer was found. While the managerial roles of Richard (Jnr) and John changed and gradually diminished, it was Anthony, as early as 1826, who was responsible for the progress of the enterprise and on the death of Richard in 1844, assumed full control. … Unlike any other Merthyr Ironmaster he provided for his workers, constructing good quality housing, building and endowing schools and churches in the villages of Troedyrhiw and Pentrebach. As recently as 1958, children in the village school at Troedyrhiw, whose grandfathers had worked in the Plymouth Collieries benefitted from a clothing grant when entering the Iocal grammar school.
To ensure the efficient continuity of the iron production, it was necessary to develop extensive coal and ironstone mines which comprised numerous adits and shafts. Almost all of these were to be found on the mountainside, feeding the works by a series of tramways and inclines. The seams exposed on the hillside were exploited by levels and drifts, while shallow pits intersected those found below the valley floor. While the ironstone mined here, like that available to the other Merthyr iron companies, was not of the highest quality, the coal was the best, with seams of bituminous and dry steam found within the property. … The year before Anthony Hill’s death, the Hill’s Plymouth Collieries mined 250,000 tons of coal, 10,000 tons more than Cyfarthfa and only 15,000 tons short of the production of the Dowlais Collieries.
Following Anthony Hill’s death, the assets of the company were acquired by Messrs Hankey, Fothergill & Bateman for a sum of £250,000, a concern that had already bought what remained of the Penydarren Ironworks which had closed in 1859. Under the enthusiastic direction of Richard Fothergill, the Aberdare Ironmaster, efforts were then made to re-vitalise the Plymouth Ironworks.
In an article written for the Mining Journal of October 1869 the virtues of this enterprise were still being proclaimed, with the mention of developing the ironmaking plant at the three sites. The author, M. B. Gardner, however is evidently more impressed with the exploitation of the property’s remaining coal reserves and mentions that ‘the area of coal leased has been greatly increased since the present proprietors purchased the works.’ Coal production we are told averaged 1,300 tons per day. … Of this output, four hundred tons were sent to Cardiff and Swansea with the rest still being used in the production of iron in the works. Eight hundred to a thousand tons of ironstone were still being mined from the property. Mr Gardner details various technical aspects of the Plymouth mines which by this time had developed in a linear fashion along the valley side, between the Plymouth and Duffryn sites and parallel with the Penydarren Tramroad.” 
This is the first and only mention in Thomas’ article of the Penydarren Tramroad. Nonetheless, it is a significant reference. It makes it clear that the Penydarren Tramroad was one of the critical factors associated with the siting of the various works which comprised the Plymouth estate. He emphasises this fact by providing a sketch drawing of the Taff Valley. The Penydarren Tramroad is the rail route which runs from top to bottom of the sketch map, to the East of Plymouth Ironworks. The Taff Valley Railway was opened in stages in 1840 and 1841.  Although the Plymouth Colliery itself opened in 1862, many of the significant industrial sites associated with the Plymouth Ironworks and Collieries had been in operation for 20 years or more before the Taff Valley Railway was completed. The Penydarren Tramroad was of significance in determining the siting of these industries in a way that the Taff Valley Railway could not have been.
Thomas highlights a number of the sites shown on the sketch above: the Ellis, Clynmill and Original pits were oldest and were mines for both coal and iron ore; the Graig, Taibach, North Duffryn and South Duffryn pits were newer and around one mile to the Southeast. All would have been in operation for about 40 years by the 1860s. Coal quality was good but extraction methods were relatively primitive. Although coal was good, iron ore was less so, and by 1875 the Plymouth Ironworks and others were in liquidation. “In 1882 the Plymouth Ironworks was for the second time advertised for sale, but once again without success. Consequently it was then possessed under a mortgage of the executors of the late Thomas Alers Hankey. … The firm of Messrs Samuel and John Bailey, Mining & Civil Engineers of Birmingham was engaged to take over the concern with Mr T. H. Bailey as agent to supervise the whole of the colliery property.” [1: p50]
T.H. Bailey kept a typed journal of his first full year in charge of the collieries. The Archive article  is based around that journal. It “offers an interesting insight into the life of a mining engineer, working at a time when the South Wales coalfield was enjoying a period of rapid development and for some, great prosperity.” [1: p51]
References are made throughout the diary to train travel on the standard gauge lines which served the valley. Bailey spends time on the internal tramways which served the mines and on providing adequate numbers of coal wagons for distributing the coal countrywide. He also dealt with the planning of new sidings to accommodate wagons and the upgrading if railway links to the main railway lines. [1: p53]
There is no mention of the Penydarren Tramroad in Bailey’s 1883 diary.
- Clive Thomas; All Change for Plymouth: A Year in the Life of a Mining Engineer, the Diary of T.H. Bailey, 1883; in Archive No. 83, Black Dwarf Lightmoor Press, Lydney, 2014, p49-61.
- https://friendsofsaron.wordpress.com/tag/hills-plymouth-company, accessed on 18th September 2019.
- https://en.m.wikipedia.org/wiki/Taff_Vale_Railway, accessed on 19th September 2019.
- http://www.alangeorge.co.uk/plymouthironworks.htm, accessed on 13th November 2019.