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Llandeilo Bridge
Afon Tywi, Llandeilo, Carmarthenshire, Wales, UK
Llandeilo Bridge
associated engineer
William Williams snr
William Williams jnr
Edward Haycock
date  1843 - 1848
UK era  Victorian  |  category  Bridge  |  reference  SN626220
ICE reference number  HEW 681
photo  Jane Joyce
The glorious single masonry arch — the longest in Wales — of Llandeilo's road bridge soars across the Afon Tywi, carrying the A483 on a falling gradient out of the Carmarthenshire town. Now heritage listed, it has been described as probably the finest single-arch bridge in Wales. It was built to replace an earlier, possibly medieval, seven-span bridge that was damaged by flooding.
A stone bridge with seven pointed arches (NPRN 23978) had been built at Llandeilo by the mid 16th century. Edwyn Jervoise, in his Ancient Bridges of Wales & Western England (1936), quotes a Tudor traveller as saying: "There was a stone bridge at Llandeilo in 1577". In 1795, the three central spans were partly destroyed by flooding and were replaced in timber. This structure was in turn washed away in 1798, and rebuilt again in timber.
By 1843, further erosion (scour) around the footings had brought the bridge near to collapse. William Williams senior, the Carmarthenshire County Bridge Surveyor, designed a new single-span masonry bridge and the contract was let to Morgan Morgan (1799-1874) of Cwmamman for £5,870, considerably below Williams' estimate of £10,000.
Work began on 4th July 1843, with 40 workmen constructing cofferdams for the removal of the old footings and construction of new abutments. On 3rd December 1844, the foundation stone was laid for the new bridge, sited on the upstream side of the old one.
Apparently, William Williams senior died in the summer of 1845, and the engineer’s role was taken over by his son, William Williams junior. Local carpenter, clerk and diarist Thomas Jenkins (1813-71) designed and constructed the timber centring for the arch, using manpower and iron derrick cranes. On 22nd October 1845, the river was in spate and swept away six of the centring supports.
Meanwhile, Morgan had failed to keep costs under control, aggravated by spiralling inflation, and he was paid off with £6,500 — £630 more than his tender price. In October 1846, the work was passed to the county’s direct labour force, supervised by Edward Haycock (1790-1870), County Surveyor of Shropshire.
On 25th November 1847, the arch was completed and the timber centring could be struck. But the masonry had settled and the centring stuck fast. Attempts to remove it with axes, saws and fire all failed. A flood three days later did the job, dislodging the supports and carrying away the timbers.
In April 1848, the rest of the old stone bridge was dismantled and the materials re-used to construct the approaches for the new bridge. Costs continued to rise, largely because limestone for the arch had had to be transported 10km from Cilyrychen Quarry in Llandybie as local stone was not suitable.
Haycock reported in October 1848, "... the bridge is now with the approaches completed in a plain and simple manner". Llandeilo Bridge had cost almost £22,000. It has a clear span of 44.1m, making it the largest in Wales and the third longest single arch in Britain. It is 1.4m longer than William Edward's (1719-89) bridge at Pontypridd, which is the second longest in Wales.
The bridge carries the A483 trunk road from the higher ground of Llandeilo over the Afon Tywi to a causeway crossing the water meadows south of the river. Buttresses standing proud of the face of the bridge and approach works support pilasters placed at each end of the bridge and at intervals along the approach walls.
The arch has an overall width of 10.1m and rises 10.7m. It is constructed in coursed masonry, using squared blocks. Most of the stonework, including the underside of the arch, the spandrels and the parapets, has been chiselled or hammer-dressed on the visible surfaces to an approximately flat finish.
The voussoirs, wedge-shaped stones that make up the outer edges of the arch, are long and narrow, and have an ashlar finish and chamfered (shaved) edges. They extend a quite a way up the faces of the bridge, meeting the string course, a horizontal band of masonry at road level, in the centre.
The bridge is now Grade II* listed.
Clerk of works: Thomas Simons of Shrewsbury
Contractor (1844-23rd October 1846): Morgan Morgan of Cwmamman
Contractor: (23rd October 1846-1848): direct labour
Timber centring: Thomas Jenkins
Research: ECPK
"Carmarthenshire and Ceredigion" by Thomas Lloyd, Julian Orbach and Robert Scourfield, Yale University Press, 2006
reference sources   CEH Wales

Llandeilo Bridge