Cannington Viaduct

This remains as the most imposing and impressive remnant of the charming 6¾-mile single-track branch line to Lyme Regis, which was promoted under the auspices of the ‘’Axminster & Lyme Regis Light Railway’’. Arthur C. Pain was appointed as independent engineer of the line and he was accompanied in this task by two of his sons, Edward and Claude, who acted as assistants. Construction of the branch commenced on 19th June 1900, a Light Railway Order having been secured in the previous year. The ‘’Light Railways Act’’ had passed successfully through Parliament in 1896 and made viable numerous local and rural railway projects, standard and narrow gauges. Essentially, the Act permitted certain minor railways to be constructed without the need to seek Royal Assent. More importantly, such railways could also be built to much lower standards than ‘’proper’’ main lines and trunk routes: line side fencing, signalling, and track curvature criteria were all relaxed. This reduced building costs substantially, but also imposed severe operating restrictions: top speeds were particularly low, and weight issues limited the range of stock that could be used. Lower building standards also had another consequence: infrastructure would wear out quickly.

The viaduct was required to span a valley 5½ route miles from Axminster, and at the time became an engineering project of some note, for it was one of few such structures to be made entirely of concrete, rather than brick. Building work was subcontracted to ‘’Baldry & Yerburgh’’ of Westminster, London (a partnership between one Henry Osborne Baldry and one John Eardley Yerburgh), and cement for the concrete was shipped in by sea to Lyme Regis Cobb. The concrete itself was the product of flint extracted from cuttings in the local area. A 1000-foot-long cableway was suspended above the valley, supported on either side by wooden pylons, and was used to move materials in place for construction. The viaduct’s design comprised ten elliptical arches of 50-foot span, the tallest of which rose to a height of 92-feet. Overall viaduct length and width were 606-feet and 16-feet respectively, and the Light Railway Order meant that the foundations were not required to penetrate deeper than 10-foot below the ground. These foundations would permit a pressure of 3½-tons per square foot to be exerted on the structure. The arches were formed using sections of pre-cast concrete, whilst the remainder of the viaduct was built using mass concrete that had not been reinforced. Unfortunately, the nature of the terrain, coupled with the need to keep construction costs low, saw Cannington Viaduct become problematic early on in its existence. The structure was built upon a surface of sandstone and clay, and before completion, the western extremity of the viaduct began to suffer from subsidence. As a result, a permanent supporting jack, also of concrete construction, had to be built within the third viaduct arch from the western embankment.

The branch line opened to traffic on 24th August 1903, and thereafter the viaduct led an unproblematic life, despite the initial incidents of subsidence. The nature of the route’s construction ensured that it was restricted to operation by small tank engines from the outset. The branch was closed completely on 29th November 1965, under Western Region auspices, when the lines west of Salisbury had entered the nadir of their fortunes. The Lyme Regis service had been operated by WR diesel multiple units since 4th November 1963.

April 1988

The impressive ten-arched viaduct is seen from its western end, looming up from the valley. Clearly in view is the jack arch, third from the left, inserted during construction as a result of structural settlement. © Mike Glasspool

April 1988

Further evidence of the branch line can be found just west of the viaduct, where a bridge fabricated from local stone is still in existence, sandwiched within the railway embankment. © Mike Glasspool