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Newport Road, Trethomas - - 372505.jpg
Newport Road, Trethomas
Grid reference: ST185885
Location: 51°35’22"N, 3°10’40"W
Post town: Caerphilly
Postcode: CF83
Dialling code: 029
Local Government
Council: Caerphilly

Trethomas otherwise Thomastown is a small village in the far west of Monmouthshire, 2½ miles north-east of Caerphilly. It neighbours Bedwas and Machen, and forms a council ward in conjunction with those communities.

Post-1900 New Town

With an original name of Thomastown, it was mainly built by William James Thomas, a co-owner of the Bedwas Navigation Colliery Company [1], (also of mines in Aberdare in the Cynon Valley). Most of the earlier parts of Trethomas were built in and around 1900-1913, when the mine was developing and at the apex of coal production in the South Wales coalfield. The terraced streets of Trethomas were appropriately named, some were named after members of William Thomas's family, hence the names: William, James, Thomas, and Mary. Others involved association with local areas, such as Navigation Street (associated with the Bedwas Navigation Colliery Company), Coronation St (for obvious reasons), Redbrook House which once stood on the left of the road entering the village from Machen opposite the Chequered Flag petrol station but was demolished in late 1950s. It was named after the brook that ran nearby and coloured red with rust from the old drift mine that was situated at Glyn Gwyn - now redeveloped as Addison Way leading up to Graig-Y-Rhacca. The bridge over the now demolished railway line on Addison Way was built on the remains of the coal tipping from that mine.


The oldest building in Trethomas, is the Ty'n-y-pwll Inn [2], known locally as the 'Pyke' due to the building being the original Toll House where tolls were charged for the use of the Toll road between Caerphilly and Newport.

The railway that ran through Trethomas went east to Newport and west to Rhymney, Merthyr Tydfil and Brecon via Talybont-on-Usk. All the lines ceased in 1961 (the loop line from White Hart to Gwern y Doman via Fountain Bridge closed in 1957) and very little remains. Nature has engulfed the two platforms from the old station and a few rotten and half buried railway sleepers sit in between. Most of what does remain of the old trackbed between Trethomas and Machen has been updated by Sustrans as a cycle-track/walkway. This starts just below the site of the old railway station in Trethomas and runs almost to where the old Machen station stood.

Nothing remains of the colliery, which closed in March 1985 during the UK miners' strike (1984-1985). The British Benzol coke ovens, which closed on Christmas Eve 1986, at the top of upper Navigation street, next to Tynywern Terraces, aptly named 'The White City' mainly because the streets and houses were always dirty due to the coke ovens being so close and the coal dust stirred up by the emptying of the wagons into the hoppers. The Colliery and what was termed 'The Plant' closed after the disastrous 84/85 Miners' Strike.

The ground on which the colliery and 'plant' stood is yet to be re-developed. The ground has reportedly high concentrations of Benzines in the soil at present and therefore it would be dangerous to re-use in its present condition. This is one major blight on the landscape. Caerphilly County Borough Council inherited most of land and face an awkward situation. To clean up the land would more than likely cost more than what the land is worth, so restoration work in the near future is unlikely. It is worthy of note that, during the 2nd World War, German aircraft actually dropped bombs, both incendiary and active, on Caerphilly Mountain top (anyone visiting the area will find it still full of craters) mistaking it for the Bedwas/Trethomas mountain where the intention was to eliminate the National Benzol 'Plant' which produced aviation fuels from the coal as by-products.

Since the demise of the Collieries further up the valley, the Rhymney River, which passes through Trethomas, has gone from being a contaminated, black monstrosity, to a clean, aromatic river, now teeming with wildlife and fish after many barren years.

At the lower end of Trethomas, close to Waterloo, a multiple-arch railway viaduct can still be seen where it used to carry the Caerphilly Branch line over the river. The old Pontypridd, Caerphilly, Newport Railway (PC & N). This railway had a loop line that allowed the heavy trains to bypass the steep incline up into Machen this line crossed the Rhymney River and through a halt named after the road bridge. The 'Fountain Bridge' on the main road between Trethomas and Waterloo. The bridge was so named because, for many years, prior to road alterations, there was a free running spring at the roadside close to the site of the bridge. The point where the spring emerged was fashioned into a stone 'fountain well' which was regrettably demolished during the road works to improve the road.

Just a few hundred yards further along the main road, once stood a large tree that stood in the middle of the junction turning to Waterloo. Locals knew it as 'The Round Tree' until it was removed during further road works. Also at the Waterloo was a Tinworks that supplied materials to the aircraft factory that once stood near the foundry above Royal Oak at Machen. Close to the Waterloo Tinworks, but on the other side of the railway became the factory that was Coates Brothers Paint Works, which later evolved into the Valspar paint division and later again became associated in the production of Inks and dyes. Nothing remains of the now demolished factory buildings.

Over many years, Trethomas has continually expanded in all directions, not only in industry, but in housing as well, so much so, that it is now difficult to find where Bedwas ends and Trethomas starts. Today notable residents include Welsh bowls captain Rosie Faulkner, former British female basketball player Cerys Sullivan, Jeff Whitefoot (Bedwas, Cardiff, Wales and British Lions rugby player) and Councillor Elizabeth Aldworth who became the Lady Mayor of Caerphilly County Borough Council in 2006.

Health research

Men from Trethomas participate in one of the world's longest running epidemiology studies - The Caerphilly Heart Disease Study. Since 1979, a representative sample of adult males born between 1918 and 1938, living in Caerphilly and the surrounding villages of Abertridwr, Bedwas, Machen, Senghenydd and Trethomas, have participated in the study. A wide range of health and lifestyle data have been collected throughout the study and have been the basis of over 400 publications in the medical press. A notable report was on the reductions in vascular disease, diabetes, congnitive impairment and dementia attributable to a healthy lifestyle.[1]


  1. The Caerphilly and Speedwell Collaborative Group. (1984 September). "Caerphilly and Speedwell collaborative heart disease studies.". Journal of Epidemiology and Public Health 38 (3): 259–262. PMID 1052363.

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