RAILWAY VENTURERS between Bodmin Parkway and Liskeard without a head for heights will find the view from 151 feet high a momentary terror, while others will enjoy the brief glimpse offered of the Glynn Valley and sprawling site of Trago Mills below a sight to behold.

After all, you won’t get a view from higher for it is Cornwall’s tallest viaduct.

However, it’s not until you find yourself looking up at St Pinnock East Viaduct that you truly appreciate the architecture that Brunel built for the Cornwall Railway.

Built in 1854 and 1855 by Isambard Kingdom Brunel as part of the efforts to link Cornwall with Plymouth and the rest of the Great Western Mainline, one which culminated in the erection of the iconic Royal Albert Bridge spanning the Tamar in 1859, while this viaduct may not be as celebrated as Brunel’s final masterpiece, it too has its own remarkable story and value in the story of Cornwall’s railway history.

Like many of Brunel’s structures in Cornwall, the St Pinnock viaduct was constructed using stone masonry with timber struts, made out of a yellow pine wood preserved by Kyansing, a chloride of mercury or, less commonly, Burnettsing, a chloride of zinc.

While the very thought of a train going across a timber supported structure might bring horror to the modern day traveller such as ourselves, when the viaducts were constructed, it wasn’t unusual, with the timber viaducts intended to be of a design where any defective timber could be withdrawn and replaced as required. It also had the benefit of keeping the costs of construction lower for the financially challenged Cornwall Railway – the finances being the reason the Royal Albert Bridge is only single-track across the Tamar.

However, the Cornwall Railway would soon find that while the cost of construction of the viaducts was cheaper because of the use of timber, it brought them a larger maintenance bill, something Brunel had warned them against. By 1875, the costs of maintaining Cornwall’s viaducts were running at over £10,000 annually.

At its outset, St Pinnock was a fairly unremarkable Class B viaduct structure. However, towards the late 1800s, the timber viaducts were in need of replacement, owing to their status as a money pit blowing a hole in the finances of the Cornwall Railway.

Replacement works began in 1875 for some of the viaducts, however for some viaducts, work wouldn’t begin until 1889 due to a dispute between Great Western Railway, who leased the line from Cornwall Railway over who would pay for the conversion to standard gauge railway.

For many of the viaduct structures, if you look carefully, you’ll notice new viaducts were built alongside the existing structures, such as at Moorswater, and you can still see the stumps of the old viaducts upon which the timber trestles would have sat.

This is where the uniqueness of St Pinnock East came in, and something which still persists to this day; for it is one of the few viaducts in Cornwall which wasn’t rebuilt from scratch but merely adapted.

In 1882, the St Pinnock viaduct would be rebuilt by raising the piers and replacing the timber with iron girders.

However, if you look carefully, you’ll see that the quality of the replacement work wasn’t quite to the standard of the original; indeed, it was done quite crudely, with tapering, sixth stage and iron girders used to replace the timber trestles.

While it might not seem it as you go over the bridge today and seemingly there isn’t enough space to swing a British Rail sandwich either side, until 1964, the St Pinnock viaduct was double-track, meaning that two trains could pass each other. However, this was changed to a single-line arrangement in order to reduce the load on and protect the viaduct, which was listed in 1985 as a Grade II listed structure.