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From the viewing area of the Tamar Bridge Visitor Centre viewing area, we get a fine view of three bridges, a traditional suspension bridge in the Tamar Bridge, a lenticular truss (a form of suspension) in the Royal Albert Bridge and a traditional arch in the Coombe viaduct, which at the time Brunel’s iron bridge was completed was actually a wooden viaduct also of his design.
There is no doubt that Isambard Kingdom Brunel was the engineer of what was then called the Saltash Bridge and it was completed in 1859 which you can see emblazoned on the end portals. It was not until the year when construction started that it took the name of Prince Albert, Queen Victoria’s consort. All of Brunel’s original drawings are labelled ‘The Saltash Bridge’ and it was built to accommodate his own broad-gauge system of railway.
Brunel had many years to think about how to construct this bridge. In 1828 he had visited the site and dismissed it, saying it was “much too wide to build a bridge”. However, by the 1840’s he had changed his views, most probably because technology improved enough to make the crossing feasible.
In August 1845 Brunel was appointed as Chief Engineer of the Cornwall Railway Company and would be responsible for connecting the South Devon Railway in Plymouth and the West Cornwall railway in the far west. Brunel decided the small town of Saltash was the most suitable spot to bridge the Tamar as it was the narrowest point at 1100ft (335.28m). By 1846 his proposal for a bridge at Saltash was accepted by the House of Lords meaning he could move forward with the project.
Brunel’s initial thoughts were to construct a timber bridge similar to the original viaduct over Coombe creek – a design he had often used to bridge the many creeks and coombes in Devon and Cornwall. To build such a structure would have meant several piers and short spans across the river.
The Admiralty expressed concern and decided the bridge should have a clearance of at least 100ft (30.48m) between the underside of the bridge and high water. They also specified a clearway on each side of the river allowing access up and down the river for Naval vessels. This meant that the structure could only have one central pier in the river. This now made a wooden structure an impossibility and new methods needed to be found.Brunel’s friend Robert Stephenson had been working with wrought iron in the construction of the square tubes on the Britannia bridge across the Menai Straits at Anglesey in Wales. As wrought iron was tough, malleable, corrosion resistant, ductile and could be formed in sheets, all of which meant it was perfect for Brunel’s proposals. Having completed a similar bridge at Chepstow in early 1853 Brunel was confident he could cross the Tamar.
And so, work begun on and on 4 July 1853 the foundation stone for the first of the Cornish piers was laid by the Mayor of Saltash at that time, Mr W Rundle, in Silver Street.
Plymouth History Festival 