Treffry Viaduct is a 19th-century architectural wonder tucked away in the Luxulyan Valley, near St Austell. It was built between 1839 and 1842 to carry both a tramway and a high-level water channel (known as a leat) across the valley for local mining entrepreneur Joseph Thomas Treffry. This was part of a local transport system designed to carry resources to the port of Par.
The first large civil engineering structure of its kind to be built in Cornwall and the only known viaduct in Britain to combine these two uses, it is now a Scheduled Monument and part of the Cornish Mining World Heritage site, as designated by UNESCO.
This feat of engineering required an expert workforce to design and build it. This included Treffry’s steward, William Pease, who is thought to have been pivotal in its planning and construction; James Meadows Rendel, one of the foremost civil engineers of the period; Henry Rowe, a stonemason and building contractor; and a host of strong, highly skilled workmen.
Treffry realised that the Luxulyan Valley was a good route between the south coast and the high ground in central Cornwall, which was being mined for tin and copper and quarried for china clay. He built a new harbour, completed in 1829, at Par, a canal up the valley to Ponts Mill and an inclined plane to the Fowey Consols mine on Penpillick Hill. To bring water power to the mine, he built a leat from Luxulyan along the west side of the valley. He also acquired the port of Newquay and land and mines in the area of Goss Moor, and planned to link them by a railway system.
Work began in 1835 on a tramway up the valley, but this was soon abandoned. Treffry then started work on a much larger-scale tramway, with an inclined plane from the canal basin at Ponts Mill, past the Carmears Rocks to the level of the top of the valley, then a level run through Luxulyan and on to its terminus at the Bugle Inn near Mollinis.
This route needed a high-level crossing of the river and so the viaduct was built. At 670 feet (204 m) long and 90 feet (27 m) high, it was the most advanced engineering project in Devon and Cornwall when it was built. It was constructed from 200,000 cubic feet of granite, which came from the nearby Carbeans and Colcerrow quarries. The lines from the quarries to the viaduct were the first parts of the tramway to be operational. The tramway was completed in 1844.
The viaduct is also an aqueduct with water running right across the structure at a lower level to the tramway. This was fed by the Charlestown Leat which it meets at the west end of the monument. The Charlestown Leat was constructed in the 1790s by Charles Rashleigh to carry water to Charlestown Harbour. Treffry formed an agreement with him that the water could be divided here so that he could use it too.
The accuracy needed for the aqueduct channel to arrive at this exact point in the valley, precisely aligned with the Charlestown Leat, is incredibly impressive for the 1840s. Following the gentlest of slopes, the water would have flowed right across the viaduct before travelling in a leat beside the tramway towards Carmears Wheel Pit. This was used to drive a water wheel, which hauled wagons up a steep slope known as an inclined plane.
The track was continued alongside the canal to Par Harbour, a project not completed until after Treffry’s death in 1850. The whole complex fell into disuse during the late 19th and early 20th centuries, and the last of Treffry’s rails were removed in 1940.
Cornwall Heritage Trust purchased Treffry Viaduct from the Treffry family in 1989. The monument is currently on the Heritage at Risk Register due to the leaks from the aqueduct channel and the resulting necessity to divert the water from flowing across the channel. Alongside Historic England, the Trust is working to secure the future of the viaduct and eventually see its removal from the Heritage at Risk Register.
The Treffry Viaduct with John Smith Documentary
In 2022, we produced a 20-minute film, which sees archaeologist and historian John Smith take viewers on a whistle-stop tour of the incredible story behind this historic monument and its beautiful surroundings.
John’s career included 23 years as Field Officer and Senior Archaeologist with Cornwall Archaeological Unit (CAU), during which time he directed a major landscape survey of the Luxulyan Valley.
The film was funded by GWR and we’re incredibly grateful for its support. We would also like to thank Jonathan and Sarah Treffry for kindly inviting us into their home and allowing us to film at Place – footage which, we hope you agree, adds a great deal of context to the story of Joseph Treffry. Our grateful thanks go to the Friends of Luxulyan Valley for allowing us to use their map of the valley and to Lightbox Studios for their hard work putting the film together. Finally, we would like to extend a huge thank you to John for his time, patience and expertise.
Plan your visit
Treffry Viaduct and the Luxulyan Valley can be reached by car, or by train via Luxulyan train station, on the Atlantic Coast railway branch line between Par and Newquay.
The viaduct can be reached on foot from Luxulyan train station by taking the following walking route. Be prepared for some parts to potentially be muddy (especially in the winter), and to climb some stiles on your way. Should you need them, you will walk by a small village shop and public toilets which are located by the church in Luxulyan.
You will partly follow the Saints’ Way – a route which is thought to have been used by early Christian pilgrims. The area is steeped in history and you will pass many remains of the industrial past on your journey, some of which you can see marked on this map.
The highlight of the walk is heading across the top of the viaduct. Its ten arches, which are 90 feet high, each have a span of 40 feet and are quite a sight to behold. This vantage point offers a spectacular view of the Luxulyan Valley. This walking trail has been created thanks to funding from GWR.
Our friends at iWalk Cornwall have also created two circular walks around the site. These are the Luxulyan Valley Circular (3.4 miles/5.5 km) and Luxulyan Valley to Prideaux (4.8 miles/7.8 km).
