Roman Road Bridge (MLN17508), Stratton St Margaret, Swindon

Summary

A skew road overbridge, with a single semi-circular arch and almost imperceptibly convex parapet line, constructed across a cutting c. 1839-40

Description

MATERIALS: faced in quarry-faced Swindon Portland stone, squared and coursed. Parapets rebuilt in purple engineering brick. The soffits refaced in the same. Also, limited patching of the faces.

DECRIPTION: skew angle is 25 degrees. Semi-circular arch with a standard span of 30ft [9m] and voussoirs, springing almost from the base of the abutments. Flanking the arch broad piers originally treated as pilasters. However, the moulded cornice which formed most of the elements of the capitals, and ran the width of each face, was replaced with a plain string course when the parapets were rebuilt. The key stones and tablet motifs were lost at the same time. Either side of the piers the faces continue as straight wing walls. A number of irregularly placed tie rods, with various styles of tie plate on both faces. The parapets terminate with piers expressed on the external face only and have a low plinth to their inside face. The coping is shallow-pitch poured concrete.

When Roman Road Bridge was constructed it was in open countryside. Today the setting has been engulfed by the suburban spread of Swindon New Town.

This list entry was subject to a Minor Amendment on 24/07/2012

History

The Great Western Railway was authorised by an Act of Parliament in 1835 to construct a line from London to Bristol. At 118 miles this was slightly longer than the other major trunk railway of its time, the London and Birmingham (112 miles) and considerably longer than other pioneering lines. Construction of the line began in 1836, using a variety of contractors and some direct labour. The first section to be completed, from London to Maidenhead Riverside (Taplow), opened in 1838, and thereafter openings followed in eight phases culminating in the completion of the whole route in 1841.

The engineering of the railway was entrusted in 1833 to Isambard Kingdom Brunel (1806-59), who was already known for his engineering projects in Bristol. More than any other railway engineer of his time he took sole responsibility for every aspect of the engineering design, from surveying the line to the detailing of buildings and structures. He sought to achieve as level a route as possible and, working from first principles, he persuaded the Directors of the GWR to adopt a broad gauge of 7ft 0¼ in rather then the standard (4ft 8½in) gauge in use on other lines. A two track broad gauge line was 30ft wide, and this determined the span of the overbridges and other structures. Except for larger bridges such as Maidenhead Bridge, the majority of Brunel’s masonry bridges did not need to be as innovative as his works in timber and iron, and his structures followed the typical architectural idioms of his time, but they were all beautifully detailed and built and together they formed integral parts of a consistently-designed pioneering railway.

Although he left no written statement concerning his design concept for the line, it can be inferred from its design and from the way it was described when opened that part of his vision was a line engineered according to picturesque principles. This influenced his selection of the route and the design of structures along it. For reasons of cost, but also because it helped blend the railway to the landscape, he used local materials for bridges and other structures, ranging from stock brick at the London end of the line, to red brick, Bath stone east of Bath and Pennant stone west of Bath. This intentional variety was remarked on by contemporaries, for instance in J.C. Bourne, 'The History and Description of the Great Western Railway' (1846).

Surviving contract drawings for bridges and other structures on this section of the line carry the signature of I.K. Brunel, reflecting his involvement with every aspect of the project. The Resident Engineer was G.E. Frere (1807-87), assisted by G.T. Clark (1809-98) and Michael Lane (1802-68), but their individual contributions have not been identified.

Roman Road Bridge was built c. 1839-40 under contract 4S on the section of the line between Challow and Wootton Bassett, which opened in December 1840. The original contract drawings survive, but are not signed.

This is the first stone bridge encountered when travelling west from London. It carries a road on the alignment of Ermin Street, the major Roman road from Gloucester (Glevum) to Silchester (Calleva Atrebatum). The form of the bridge is unique on the line, with a semi-circular arch springing almost from rail level, quarry-faced stone elevations and originally a classical tablet motif in the centre of each parapet. Although his intentions are not recorded, it is possible that Brunel took his inspiration for the design and its classical vocabulary from the Roman origins of the road which it carried (the Romans invented the arch, and semi-circular arches are characteristic of their viaducts and bridges).

This stretch of the line was never quadrupled and so the bridge has not been extended. However, in the C20 the parapets, soffits and some patches were refaced in engineering brick. A number of tie rods were also inserted. In 1956 a steel footbridge was built alongside on the west (high mileage) side.

Reasons for Listing

Roman Road Bridge, Stratton St Margaret in Swindon which was constructed c.1839-40 and carries Ermin Street over the GWML, is designated at Grade II for following principal reasons:
* Date: an early example of a railway structure dating from the pioneering phase in national railway development on this significant line;
* Design interest: the original design, in Brunel's hand, makes architectural reference to the Roman Road that this overbridge was constructed to carry over the Great Western Railway;
* Material interest: the use of local Swindon Portland stone, quarry-faced to suggest a rugged antiquity, illustrates the changing geology and materials along the route of the railway and marks the passage of the line into a stone area, thus witnessing Brunel's skilful attention to picturesque principles;
* Legibility: although regrettably the parapets, cornice and pair of classical tablets have been replaced in engineering brick, the apposite and unique employment of a semi-circular arch (referring to the Roman invention of the same) survives; were the original design to survive completely, a higher grade would be warranted.

External Links

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